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• Primary vs secondary sources: The differences explained 

Can something be both a primary and secondary source?

Research for your literature review can be categorised as either primary or secondary in nature. The simplest definition of primary sources is either original information (such as survey data) or a first person account of an event (such as an interview transcript). Whereas secondary sources are any publshed or unpublished works that describe, summarise, analyse, evaluate, interpret or review primary source materials. Secondary sources can incorporate primary sources to support their arguments.

Ideally, good research should use a combination of both primary and secondary sources. For example, if a researcher were to investigate the introduction of a law and the impacts it had on a community, he/she might look at the transcripts of the parliamentary debates as well as the parliamentary commentary and news reporting surrounding the laws at the time. 

Examples of primary and secondary sources

Primary vs secondary sources: The differences explained

Finding primary sources

• VU Special Collections  - The Special Collections at Victoria University Library are a valuable research resource. The Collections have strong threads of radical literature, particularly Australian Communist literature, much of which is rare or unique. Women and urban planning also feature across the Collections. There are collections that give you a picture of the people who donated them like Ray Verrills, John McLaren, Sir Zelman Cowen, and Ruth & Maurie Crow. Other collections focus on Australia's neighbours – PNG and Timor-Leste.
• POLICY - Sharing the latest in policy knowledge and evidence, this database supports enhanced learning, collaboration and contribution.
• Indigenous Australia  -  The Indigenous Australia database represents the collections of the Aboriginal and Torres Strait Islander Commission Library.
• Australian Heritage Bibliography - Aboriginal and Torres Strait Islander Subset (AHB-ATSIS)  - AHB is a bibliographic database that indexes and abstracts articles from published and unpublished material on Australia's natural and cultural environment. The AHB-ATSIS subset contains records that specifically relate to the Aboriginal and Torres Strait Islander peoples.include journal articles, unpublished reports, books, videos and conference proceedings from many different sources around Australia. Emphasis is placed on reports written or commissioned by government and non-government heritage agencies throughout the country.
• ATSIhealth  - The Aboriginal and Torres Strait Islander Health Bibliography (ATSIhealth), compiled by Neil Thomson and Natalie Weissofner at the School of Indigenous Australian Studies, Kurongkurl Katitjin, Edith Cowan University, is a bibliographic database that indexes published and unpublished material on Australian Indigenous health. Source documents include theses, unpublished articles, government reports, conference papers, abstracts, book chapters, books, discussion and working papers, and statistical documents. 
• National Archive of Australia  - The National Archives of Australia holds the memory of our nation and keeps vital Australian Government records safe. 
• National Library of Australia: Manuscripts  - Manuscripts collection that is wide ranging and provides rich evidence of the lives and activities of Australians who have shaped our society.
• National Library of Australia: Printed ephemera  - The National Library has been selectively collecting Australian printed ephemera since the early 1960s as a record of Australian life and social customs, popular culture, national events, and issues of national concern.
• National Library of Australia: Oral history and folklore - The Library’s Oral History and Folklore Collection dates back to the 1950’s and includes a rich and diverse collection of interviews and recordings with Australians from all walks of life.
• Historic Hansard - Commonwealth of Australia parliamentary debates presented in an easy-to-read format for historians and other lovers of political speech.
• The Old Bailey Online - A fully searchable edition of the largest body of texts detailing the lives of non-elite people ever published, containing 197,745 criminal trials held at London's central criminal court.

Whether or not a source can be considered both primary and  secondary, depends on the context. In some instances, material may act as a secondary source for one research area, and as a primary source for another. For example, Niccolò Machiavelli’s The Prince , published in 1513, is an important secondary source for any study of the various Renaissance princes in the Medici family; but the same book is also a primary source for the political thought that was characteristic of the sixteenth century because it reflects the attitudes of a person living in the 1500s.

Source: Craver, 1999, as cited in University of South Australia Library. (2021, Oct 6).  Can something be a primary and secondary source?.  University of South Australia Library. https://guides.library.unisa.edu.au/historycultural/sourcetypes

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The Literature

The Literature refers to the collection of scholarly writings on a topic. This includes peer-reviewed articles, books, dissertations and conference papers.

• When reviewing the literature, be sure to include major works as well as studies that respond to major works. You will want to focus on primary sources, though secondary sources can be valuable as well.

Primary Sources

The term primary source is used broadly to embody all sources that are original. P rimary sources provide first-hand information that is closest to the object of study. Primary sources vary by discipline.

• In the natural and social sciences, original reports of research found in academic journals detailing the methodology used in the research, in-depth descriptions, and discussions of the findings are considered primary sources of information.
• Other common examples of primary sources include speeches, letters, diaries, autobiographies, interviews, official reports, court records, artifacts, photographs, and drawings.  

Galvan, J. L. (2013). Writing literature reviews: A guide for students of the social and behavioral sciences . Glendale, CA: Pyrczak.

Secondary Sources

A secondary source is a source that provides non-original or secondhand data or information. 

• Secondary sources are written about primary sources.
• Research summaries reported in textbooks, magazines, and newspapers are considered secondary sources. They typically provide global descriptions of results with few details on the methodology. Other examples of secondary sources include biographies and critical studies of an author's work.

Secondary Source. (2005). In W. Paul Vogt (Ed.), Dictionary of Statistics & Methodology. (3 rd ed., p. 291). Thousand Oaks, CA: SAGE Publications, Inc.

Weidenborner, S., & Caruso, D. (1997). Writing research papers: A guide to the process . New York: St. Martin's Press.

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Writing a Literature Review

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A literature review is a document or section of a document that collects key sources on a topic and discusses those sources in conversation with each other (also called synthesis ). The lit review is an important genre in many disciplines, not just literature (i.e., the study of works of literature such as novels and plays). When we say “literature review” or refer to “the literature,” we are talking about the research ( scholarship ) in a given field. You will often see the terms “the research,” “the scholarship,” and “the literature” used mostly interchangeably.

Where, when, and why would I write a lit review?

There are a number of different situations where you might write a literature review, each with slightly different expectations; different disciplines, too, have field-specific expectations for what a literature review is and does. For instance, in the humanities, authors might include more overt argumentation and interpretation of source material in their literature reviews, whereas in the sciences, authors are more likely to report study designs and results in their literature reviews; these differences reflect these disciplines’ purposes and conventions in scholarship. You should always look at examples from your own discipline and talk to professors or mentors in your field to be sure you understand your discipline’s conventions, for literature reviews as well as for any other genre.

A literature review can be a part of a research paper or scholarly article, usually falling after the introduction and before the research methods sections. In these cases, the lit review just needs to cover scholarship that is important to the issue you are writing about; sometimes it will also cover key sources that informed your research methodology.

Lit reviews can also be standalone pieces, either as assignments in a class or as publications. In a class, a lit review may be assigned to help students familiarize themselves with a topic and with scholarship in their field, get an idea of the other researchers working on the topic they’re interested in, find gaps in existing research in order to propose new projects, and/or develop a theoretical framework and methodology for later research. As a publication, a lit review usually is meant to help make other scholars’ lives easier by collecting and summarizing, synthesizing, and analyzing existing research on a topic. This can be especially helpful for students or scholars getting into a new research area, or for directing an entire community of scholars toward questions that have not yet been answered.

What are the parts of a lit review?

Most lit reviews use a basic introduction-body-conclusion structure; if your lit review is part of a larger paper, the introduction and conclusion pieces may be just a few sentences while you focus most of your attention on the body. If your lit review is a standalone piece, the introduction and conclusion take up more space and give you a place to discuss your goals, research methods, and conclusions separately from where you discuss the literature itself.

Introduction:

• An introductory paragraph that explains what your working topic and thesis is
• A forecast of key topics or texts that will appear in the review
• Potentially, a description of how you found sources and how you analyzed them for inclusion and discussion in the review (more often found in published, standalone literature reviews than in lit review sections in an article or research paper)
• Summarize and synthesize: Give an overview of the main points of each source and combine them into a coherent whole
• Analyze and interpret: Don’t just paraphrase other researchers – add your own interpretations where possible, discussing the significance of findings in relation to the literature as a whole
• Critically Evaluate: Mention the strengths and weaknesses of your sources
• Write in well-structured paragraphs: Use transition words and topic sentence to draw connections, comparisons, and contrasts.

Conclusion:

• Summarize the key findings you have taken from the literature and emphasize their significance
• Connect it back to your primary research question

How should I organize my lit review?

Lit reviews can take many different organizational patterns depending on what you are trying to accomplish with the review. Here are some examples:

• Chronological : The simplest approach is to trace the development of the topic over time, which helps familiarize the audience with the topic (for instance if you are introducing something that is not commonly known in your field). If you choose this strategy, be careful to avoid simply listing and summarizing sources in order. Try to analyze the patterns, turning points, and key debates that have shaped the direction of the field. Give your interpretation of how and why certain developments occurred (as mentioned previously, this may not be appropriate in your discipline — check with a teacher or mentor if you’re unsure).
• Thematic : If you have found some recurring central themes that you will continue working with throughout your piece, you can organize your literature review into subsections that address different aspects of the topic. For example, if you are reviewing literature about women and religion, key themes can include the role of women in churches and the religious attitude towards women.
• Qualitative versus quantitative research
• Empirical versus theoretical scholarship
• Divide the research by sociological, historical, or cultural sources
• Theoretical : In many humanities articles, the literature review is the foundation for the theoretical framework. You can use it to discuss various theories, models, and definitions of key concepts. You can argue for the relevance of a specific theoretical approach or combine various theorical concepts to create a framework for your research.

What are some strategies or tips I can use while writing my lit review?

Any lit review is only as good as the research it discusses; make sure your sources are well-chosen and your research is thorough. Don’t be afraid to do more research if you discover a new thread as you’re writing. More info on the research process is available in our "Conducting Research" resources .

As you’re doing your research, create an annotated bibliography ( see our page on the this type of document ). Much of the information used in an annotated bibliography can be used also in a literature review, so you’ll be not only partially drafting your lit review as you research, but also developing your sense of the larger conversation going on among scholars, professionals, and any other stakeholders in your topic.

Usually you will need to synthesize research rather than just summarizing it. This means drawing connections between sources to create a picture of the scholarly conversation on a topic over time. Many student writers struggle to synthesize because they feel they don’t have anything to add to the scholars they are citing; here are some strategies to help you:

• It often helps to remember that the point of these kinds of syntheses is to show your readers how you understand your research, to help them read the rest of your paper.
• Writing teachers often say synthesis is like hosting a dinner party: imagine all your sources are together in a room, discussing your topic. What are they saying to each other?
• Look at the in-text citations in each paragraph. Are you citing just one source for each paragraph? This usually indicates summary only. When you have multiple sources cited in a paragraph, you are more likely to be synthesizing them (not always, but often
• Read more about synthesis here.

The most interesting literature reviews are often written as arguments (again, as mentioned at the beginning of the page, this is discipline-specific and doesn’t work for all situations). Often, the literature review is where you can establish your research as filling a particular gap or as relevant in a particular way. You have some chance to do this in your introduction in an article, but the literature review section gives a more extended opportunity to establish the conversation in the way you would like your readers to see it. You can choose the intellectual lineage you would like to be part of and whose definitions matter most to your thinking (mostly humanities-specific, but this goes for sciences as well). In addressing these points, you argue for your place in the conversation, which tends to make the lit review more compelling than a simple reporting of other sources.

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• How to Write a Literature Review | Guide, Examples, & Templates

How to Write a Literature Review | Guide, Examples, & Templates

Published on January 2, 2023 by Shona McCombes . Revised on September 11, 2023.

What is a literature review? A literature review is a survey of scholarly sources on a specific topic. It provides an overview of current knowledge, allowing you to identify relevant theories, methods, and gaps in the existing research that you can later apply to your paper, thesis, or dissertation topic .

There are five key steps to writing a literature review:

• Search for relevant literature
• Evaluate sources
• Identify themes, debates, and gaps
• Outline the structure
• Write your literature review

A good literature review doesn’t just summarize sources—it analyzes, synthesizes , and critically evaluates to give a clear picture of the state of knowledge on the subject.

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Table of contents

What is the purpose of a literature review, examples of literature reviews, step 1 – search for relevant literature, step 2 – evaluate and select sources, step 3 – identify themes, debates, and gaps, step 4 – outline your literature review’s structure, step 5 – write your literature review, free lecture slides, other interesting articles, frequently asked questions, introduction.

• Quick Run-through
• Step 1 & 2

When you write a thesis , dissertation , or research paper , you will likely have to conduct a literature review to situate your research within existing knowledge. The literature review gives you a chance to:

• Demonstrate your familiarity with the topic and its scholarly context
• Develop a theoretical framework and methodology for your research
• Position your work in relation to other researchers and theorists
• Show how your research addresses a gap or contributes to a debate
• Evaluate the current state of research and demonstrate your knowledge of the scholarly debates around your topic.

Writing literature reviews is a particularly important skill if you want to apply for graduate school or pursue a career in research. We’ve written a step-by-step guide that you can follow below.

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See an example

Writing literature reviews can be quite challenging! A good starting point could be to look at some examples, depending on what kind of literature review you’d like to write.

• Example literature review #1: “Why Do People Migrate? A Review of the Theoretical Literature” ( Theoretical literature review about the development of economic migration theory from the 1950s to today.)
• Example literature review #2: “Literature review as a research methodology: An overview and guidelines” ( Methodological literature review about interdisciplinary knowledge acquisition and production.)
• Example literature review #3: “The Use of Technology in English Language Learning: A Literature Review” ( Thematic literature review about the effects of technology on language acquisition.)
• Example literature review #4: “Learners’ Listening Comprehension Difficulties in English Language Learning: A Literature Review” ( Chronological literature review about how the concept of listening skills has changed over time.)

You can also check out our templates with literature review examples and sample outlines at the links below.

Download Word doc Download Google doc

Before you begin searching for literature, you need a clearly defined topic .

If you are writing the literature review section of a dissertation or research paper, you will search for literature related to your research problem and questions .

Make a list of keywords

Start by creating a list of keywords related to your research question. Include each of the key concepts or variables you’re interested in, and list any synonyms and related terms. You can add to this list as you discover new keywords in the process of your literature search.

• Social media, Facebook, Instagram, Twitter, Snapchat, TikTok
• Body image, self-perception, self-esteem, mental health
• Generation Z, teenagers, adolescents, youth

Search for relevant sources

Use your keywords to begin searching for sources. Some useful databases to search for journals and articles include:

• Your university’s library catalogue
• Google Scholar
• Project Muse (humanities and social sciences)
• Medline (life sciences and biomedicine)
• EconLit (economics)
• Inspec (physics, engineering and computer science)

You can also use boolean operators to help narrow down your search.

Make sure to read the abstract to find out whether an article is relevant to your question. When you find a useful book or article, you can check the bibliography to find other relevant sources.

You likely won’t be able to read absolutely everything that has been written on your topic, so it will be necessary to evaluate which sources are most relevant to your research question.

For each publication, ask yourself:

• What question or problem is the author addressing?
• What are the key concepts and how are they defined?
• What are the key theories, models, and methods?
• Does the research use established frameworks or take an innovative approach?
• What are the results and conclusions of the study?
• How does the publication relate to other literature in the field? Does it confirm, add to, or challenge established knowledge?
• What are the strengths and weaknesses of the research?

Make sure the sources you use are credible , and make sure you read any landmark studies and major theories in your field of research.

You can use our template to summarize and evaluate sources you’re thinking about using. Click on either button below to download.

Take notes and cite your sources

As you read, you should also begin the writing process. Take notes that you can later incorporate into the text of your literature review.

It is important to keep track of your sources with citations to avoid plagiarism . It can be helpful to make an annotated bibliography , where you compile full citation information and write a paragraph of summary and analysis for each source. This helps you remember what you read and saves time later in the process.

To begin organizing your literature review’s argument and structure, be sure you understand the connections and relationships between the sources you’ve read. Based on your reading and notes, you can look for:

• Trends and patterns (in theory, method or results): do certain approaches become more or less popular over time?
• Themes: what questions or concepts recur across the literature?
• Debates, conflicts and contradictions: where do sources disagree?
• Pivotal publications: are there any influential theories or studies that changed the direction of the field?
• Gaps: what is missing from the literature? Are there weaknesses that need to be addressed?

This step will help you work out the structure of your literature review and (if applicable) show how your own research will contribute to existing knowledge.

• Most research has focused on young women.
• There is an increasing interest in the visual aspects of social media.
• But there is still a lack of robust research on highly visual platforms like Instagram and Snapchat—this is a gap that you could address in your own research.

There are various approaches to organizing the body of a literature review. Depending on the length of your literature review, you can combine several of these strategies (for example, your overall structure might be thematic, but each theme is discussed chronologically).

Chronological

The simplest approach is to trace the development of the topic over time. However, if you choose this strategy, be careful to avoid simply listing and summarizing sources in order.

Try to analyze patterns, turning points and key debates that have shaped the direction of the field. Give your interpretation of how and why certain developments occurred.

If you have found some recurring central themes, you can organize your literature review into subsections that address different aspects of the topic.

For example, if you are reviewing literature about inequalities in migrant health outcomes, key themes might include healthcare policy, language barriers, cultural attitudes, legal status, and economic access.

Methodological

If you draw your sources from different disciplines or fields that use a variety of research methods , you might want to compare the results and conclusions that emerge from different approaches. For example:

• Look at what results have emerged in qualitative versus quantitative research
• Discuss how the topic has been approached by empirical versus theoretical scholarship
• Divide the literature into sociological, historical, and cultural sources

Theoretical

A literature review is often the foundation for a theoretical framework . You can use it to discuss various theories, models, and definitions of key concepts.

You might argue for the relevance of a specific theoretical approach, or combine various theoretical concepts to create a framework for your research.

Like any other academic text , your literature review should have an introduction , a main body, and a conclusion . What you include in each depends on the objective of your literature review.

The introduction should clearly establish the focus and purpose of the literature review.

Depending on the length of your literature review, you might want to divide the body into subsections. You can use a subheading for each theme, time period, or methodological approach.

As you write, you can follow these tips:

• Summarize and synthesize: give an overview of the main points of each source and combine them into a coherent whole
• Analyze and interpret: don’t just paraphrase other researchers — add your own interpretations where possible, discussing the significance of findings in relation to the literature as a whole
• Critically evaluate: mention the strengths and weaknesses of your sources
• Write in well-structured paragraphs: use transition words and topic sentences to draw connections, comparisons and contrasts

In the conclusion, you should summarize the key findings you have taken from the literature and emphasize their significance.

When you’ve finished writing and revising your literature review, don’t forget to proofread thoroughly before submitting. Not a language expert? Check out Scribbr’s professional proofreading services !

This article has been adapted into lecture slides that you can use to teach your students about writing a literature review.

Scribbr slides are free to use, customize, and distribute for educational purposes.

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If you want to know more about the research process , methodology , research bias , or statistics , make sure to check out some of our other articles with explanations and examples.

• Sampling methods
• Simple random sampling
• Stratified sampling
• Cluster sampling
• Likert scales
• Reproducibility

 Statistics

• Null hypothesis
• Statistical power
• Probability distribution
• Effect size
• Poisson distribution

Research bias

• Optimism bias
• Cognitive bias
• Implicit bias
• Hawthorne effect
• Anchoring bias
• Explicit bias

A literature review is a survey of scholarly sources (such as books, journal articles, and theses) related to a specific topic or research question .

It is often written as part of a thesis, dissertation , or research paper , in order to situate your work in relation to existing knowledge.

There are several reasons to conduct a literature review at the beginning of a research project:

• To familiarize yourself with the current state of knowledge on your topic
• To ensure that you’re not just repeating what others have already done
• To identify gaps in knowledge and unresolved problems that your research can address
• To develop your theoretical framework and methodology
• To provide an overview of the key findings and debates on the topic

Writing the literature review shows your reader how your work relates to existing research and what new insights it will contribute.

The literature review usually comes near the beginning of your thesis or dissertation . After the introduction , it grounds your research in a scholarly field and leads directly to your theoretical framework or methodology .

A literature review is a survey of credible sources on a topic, often used in dissertations , theses, and research papers . Literature reviews give an overview of knowledge on a subject, helping you identify relevant theories and methods, as well as gaps in existing research. Literature reviews are set up similarly to other  academic texts , with an introduction , a main body, and a conclusion .

An  annotated bibliography is a list of  source references that has a short description (called an annotation ) for each of the sources. It is often assigned as part of the research process for a  paper .  

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Primary Sources are the Leading Edge

Primary sources are the leading edge of research-- the first discussion of what is going on in the field, in the sciences and sometimes in the social sciences. They will use other publications as support, but contribute new knowledge to the scholarly conversation. But historians and scholars of literature and art think of primary works differently-- see below.

What's a Primary Source? Information in the Various Disciplines

What is considered a primary source varies somewhat by discipline. In any case, think of a primary source as first-hand knowledge, eyewitness accounts, reports or testimony about (X topic).

In the fields commonly considered sciences, a primary source is the first report of research, published as a journal article, a research report or conference proceeding, or if extensive, a book or book chapter. They include methodology, data and results, and discussion.

In social sciences, such as anthropology, ethnography, psychology, sociology or social work, a primary source may be the first report of research, especially of empirical studies, or, since some areas of these fields depend on direct observation of behavior or analysis of interviews or personal narratives, the products of this analysis may still be considered a primary work. For history, and in some other disciplines, a primary source is a letter, a diary, speech, lecture, piece of legislation, document or manuscript-- an original source which forms the basis of secondary work. A narrative is a personal account, by a single individual, of a period of time or an event. In the arts, a primary source may be a piece of art, such as a painting or sculpture, a musical score, a poem, a book or chapter, or an essay--whatever is directly created by the artist, writer, photographer, etc.

A secondary source is based on other sources. It includes analysis, criticism, or other intellectual input. Review articles are based on analysis of the published 'literature' (books, articles and dissertations about the topic). Secondary sources can include books, book chapters, articles, especially literature reviews, and some book reviews.

A tertiary source is commonly a resource or tool that helps people find primary or secondary sources. Tertiary sources include most bibliographies, databases and indexes, and library catalogs.

What are Primary Sources?

Here's a great definition from the American Library Association:

"Primary sources are original records created at the time historical events occurred or well after events in the form of memoirs and oral histories. Primary sources may include letters, manuscripts, diaries, journals, newspapers, speeches, interviews, memoirs, documents produced by government agencies such as Congress or the Office of the President, photographs, audio recordings, moving pictures or video recordings, research data, and objects or artifacts such as works of art or ancient roads, buildings, tools, and weapons. These sources serve as the raw material to interpret the past, and when they are used along with previous interpretations by historians, they provide the resources necessary for historical research."

-- Using Primary Sources on the Web , rev. 2008.

Peer-reviewed/Scholarly?

Peer review is the process by which articles or other works are critiqued before they are published. Authors send articles to an editor, who decides whether the work should be forwarded to reviewers for the journal. The most stringent form is anonymous or blind review, where neither the author nor the reviewers know whose work is being examined by whom. This helps reduce bias.

Reviewers are usually well-published researchers and experts. They return the articles to the editor with remarks and recommendations-- usually publish as is (rare), publish if edited or changed in specific ways, or don't publish. Editors most often go with the recommendation of the majority of the reviewers.

The process is intended to improve the studies published-- more eyes on a project, and one's reputation on the line with peers, tends to improve the quality of what's published. There are cases where it hasn't worked, and critics of the peer review cycle (some claim that it limits innovative studies, among other issues), but it is the best system that has been developed to this point.

Peer-reviewed or referreed or scholarly are often descriptions used interchangably for reputable journals. Not all scholarly journals are peer-reviewed, but many are.

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A literature review surveys prior research published in books, scholarly articles, and any other sources relevant to a particular issue, area of research, or theory, and by so doing, provides a description, summary, and critical evaluation of these works in relation to the research problem being investigated. Literature reviews are designed to provide an overview of sources you have used in researching a particular topic and to demonstrate to your readers how your research fits within existing scholarship about the topic.

Fink, Arlene. Conducting Research Literature Reviews: From the Internet to Paper . Fourth edition. Thousand Oaks, CA: SAGE, 2014.

Importance of a Good Literature Review

A literature review may consist of simply a summary of key sources, but in the social sciences, a literature review usually has an organizational pattern and combines both summary and synthesis, often within specific conceptual categories . A summary is a recap of the important information of the source, but a synthesis is a re-organization, or a reshuffling, of that information in a way that informs how you are planning to investigate a research problem. The analytical features of a literature review might:

• Give a new interpretation of old material or combine new with old interpretations,
• Trace the intellectual progression of the field, including major debates,
• Depending on the situation, evaluate the sources and advise the reader on the most pertinent or relevant research, or
• Usually in the conclusion of a literature review, identify where gaps exist in how a problem has been researched to date.

Given this, the purpose of a literature review is to:

• Place each work in the context of its contribution to understanding the research problem being studied.
• Describe the relationship of each work to the others under consideration.
• Identify new ways to interpret prior research.
• Reveal any gaps that exist in the literature.
• Resolve conflicts amongst seemingly contradictory previous studies.
• Identify areas of prior scholarship to prevent duplication of effort.
• Point the way in fulfilling a need for additional research.
• Locate your own research within the context of existing literature [very important].

Fink, Arlene. Conducting Research Literature Reviews: From the Internet to Paper. 2nd ed. Thousand Oaks, CA: Sage, 2005; Hart, Chris. Doing a Literature Review: Releasing the Social Science Research Imagination . Thousand Oaks, CA: Sage Publications, 1998; Jesson, Jill. Doing Your Literature Review: Traditional and Systematic Techniques . Los Angeles, CA: SAGE, 2011; Knopf, Jeffrey W. "Doing a Literature Review." PS: Political Science and Politics 39 (January 2006): 127-132; Ridley, Diana. The Literature Review: A Step-by-Step Guide for Students . 2nd ed. Los Angeles, CA: SAGE, 2012.

Types of Literature Reviews

It is important to think of knowledge in a given field as consisting of three layers. First, there are the primary studies that researchers conduct and publish. Second are the reviews of those studies that summarize and offer new interpretations built from and often extending beyond the primary studies. Third, there are the perceptions, conclusions, opinion, and interpretations that are shared informally among scholars that become part of the body of epistemological traditions within the field.

In composing a literature review, it is important to note that it is often this third layer of knowledge that is cited as "true" even though it often has only a loose relationship to the primary studies and secondary literature reviews. Given this, while literature reviews are designed to provide an overview and synthesis of pertinent sources you have explored, there are a number of approaches you could adopt depending upon the type of analysis underpinning your study.

Argumentative Review This form examines literature selectively in order to support or refute an argument, deeply embedded assumption, or philosophical problem already established in the literature. The purpose is to develop a body of literature that establishes a contrarian viewpoint. Given the value-laden nature of some social science research [e.g., educational reform; immigration control], argumentative approaches to analyzing the literature can be a legitimate and important form of discourse. However, note that they can also introduce problems of bias when they are used to make summary claims of the sort found in systematic reviews [see below].

Integrative Review Considered a form of research that reviews, critiques, and synthesizes representative literature on a topic in an integrated way such that new frameworks and perspectives on the topic are generated. The body of literature includes all studies that address related or identical hypotheses or research problems. A well-done integrative review meets the same standards as primary research in regard to clarity, rigor, and replication. This is the most common form of review in the social sciences.

Historical Review Few things rest in isolation from historical precedent. Historical literature reviews focus on examining research throughout a period of time, often starting with the first time an issue, concept, theory, phenomena emerged in the literature, then tracing its evolution within the scholarship of a discipline. The purpose is to place research in a historical context to show familiarity with state-of-the-art developments and to identify the likely directions for future research.

Methodological Review A review does not always focus on what someone said [findings], but how they came about saying what they say [method of analysis]. Reviewing methods of analysis provides a framework of understanding at different levels [i.e. those of theory, substantive fields, research approaches, and data collection and analysis techniques], how researchers draw upon a wide variety of knowledge ranging from the conceptual level to practical documents for use in fieldwork in the areas of ontological and epistemological consideration, quantitative and qualitative integration, sampling, interviewing, data collection, and data analysis. This approach helps highlight ethical issues which you should be aware of and consider as you go through your own study.

Systematic Review This form consists of an overview of existing evidence pertinent to a clearly formulated research question, which uses pre-specified and standardized methods to identify and critically appraise relevant research, and to collect, report, and analyze data from the studies that are included in the review. The goal is to deliberately document, critically evaluate, and summarize scientifically all of the research about a clearly defined research problem . Typically it focuses on a very specific empirical question, often posed in a cause-and-effect form, such as "To what extent does A contribute to B?" This type of literature review is primarily applied to examining prior research studies in clinical medicine and allied health fields, but it is increasingly being used in the social sciences.

Theoretical Review The purpose of this form is to examine the corpus of theory that has accumulated in regard to an issue, concept, theory, phenomena. The theoretical literature review helps to establish what theories already exist, the relationships between them, to what degree the existing theories have been investigated, and to develop new hypotheses to be tested. Often this form is used to help establish a lack of appropriate theories or reveal that current theories are inadequate for explaining new or emerging research problems. The unit of analysis can focus on a theoretical concept or a whole theory or framework.

NOTE: Most often the literature review will incorporate some combination of types. For example, a review that examines literature supporting or refuting an argument, assumption, or philosophical problem related to the research problem will also need to include writing supported by sources that establish the history of these arguments in the literature.

Baumeister, Roy F. and Mark R. Leary. "Writing Narrative Literature Reviews."  Review of General Psychology 1 (September 1997): 311-320; Mark R. Fink, Arlene. Conducting Research Literature Reviews: From the Internet to Paper . 2nd ed. Thousand Oaks, CA: Sage, 2005; Hart, Chris. Doing a Literature Review: Releasing the Social Science Research Imagination . Thousand Oaks, CA: Sage Publications, 1998; Kennedy, Mary M. "Defining a Literature." Educational Researcher 36 (April 2007): 139-147; Petticrew, Mark and Helen Roberts. Systematic Reviews in the Social Sciences: A Practical Guide . Malden, MA: Blackwell Publishers, 2006; Torracro, Richard. "Writing Integrative Literature Reviews: Guidelines and Examples." Human Resource Development Review 4 (September 2005): 356-367; Rocco, Tonette S. and Maria S. Plakhotnik. "Literature Reviews, Conceptual Frameworks, and Theoretical Frameworks: Terms, Functions, and Distinctions." Human Ressource Development Review 8 (March 2008): 120-130; Sutton, Anthea. Systematic Approaches to a Successful Literature Review . Los Angeles, CA: Sage Publications, 2016.

Structure and Writing Style

I.  Thinking About Your Literature Review

The structure of a literature review should include the following in support of understanding the research problem :

• An overview of the subject, issue, or theory under consideration, along with the objectives of the literature review,
• Division of works under review into themes or categories [e.g. works that support a particular position, those against, and those offering alternative approaches entirely],
• An explanation of how each work is similar to and how it varies from the others,
• Conclusions as to which pieces are best considered in their argument, are most convincing of their opinions, and make the greatest contribution to the understanding and development of their area of research.

The critical evaluation of each work should consider :

• Provenance -- what are the author's credentials? Are the author's arguments supported by evidence [e.g. primary historical material, case studies, narratives, statistics, recent scientific findings]?
• Methodology -- were the techniques used to identify, gather, and analyze the data appropriate to addressing the research problem? Was the sample size appropriate? Were the results effectively interpreted and reported?
• Objectivity -- is the author's perspective even-handed or prejudicial? Is contrary data considered or is certain pertinent information ignored to prove the author's point?
• Persuasiveness -- which of the author's theses are most convincing or least convincing?
• Validity -- are the author's arguments and conclusions convincing? Does the work ultimately contribute in any significant way to an understanding of the subject?

II.  Development of the Literature Review

Four Basic Stages of Writing 1.  Problem formulation -- which topic or field is being examined and what are its component issues? 2.  Literature search -- finding materials relevant to the subject being explored. 3.  Data evaluation -- determining which literature makes a significant contribution to the understanding of the topic. 4.  Analysis and interpretation -- discussing the findings and conclusions of pertinent literature.

Consider the following issues before writing the literature review: Clarify If your assignment is not specific about what form your literature review should take, seek clarification from your professor by asking these questions: 1.  Roughly how many sources would be appropriate to include? 2.  What types of sources should I review (books, journal articles, websites; scholarly versus popular sources)? 3.  Should I summarize, synthesize, or critique sources by discussing a common theme or issue? 4.  Should I evaluate the sources in any way beyond evaluating how they relate to understanding the research problem? 5.  Should I provide subheadings and other background information, such as definitions and/or a history? Find Models Use the exercise of reviewing the literature to examine how authors in your discipline or area of interest have composed their literature review sections. Read them to get a sense of the types of themes you might want to look for in your own research or to identify ways to organize your final review. The bibliography or reference section of sources you've already read, such as required readings in the course syllabus, are also excellent entry points into your own research. Narrow the Topic The narrower your topic, the easier it will be to limit the number of sources you need to read in order to obtain a good survey of relevant resources. Your professor will probably not expect you to read everything that's available about the topic, but you'll make the act of reviewing easier if you first limit scope of the research problem. A good strategy is to begin by searching the USC Libraries Catalog for recent books about the topic and review the table of contents for chapters that focuses on specific issues. You can also review the indexes of books to find references to specific issues that can serve as the focus of your research. For example, a book surveying the history of the Israeli-Palestinian conflict may include a chapter on the role Egypt has played in mediating the conflict, or look in the index for the pages where Egypt is mentioned in the text. Consider Whether Your Sources are Current Some disciplines require that you use information that is as current as possible. This is particularly true in disciplines in medicine and the sciences where research conducted becomes obsolete very quickly as new discoveries are made. However, when writing a review in the social sciences, a survey of the history of the literature may be required. In other words, a complete understanding the research problem requires you to deliberately examine how knowledge and perspectives have changed over time. Sort through other current bibliographies or literature reviews in the field to get a sense of what your discipline expects. You can also use this method to explore what is considered by scholars to be a "hot topic" and what is not.

III.  Ways to Organize Your Literature Review

Chronology of Events If your review follows the chronological method, you could write about the materials according to when they were published. This approach should only be followed if a clear path of research building on previous research can be identified and that these trends follow a clear chronological order of development. For example, a literature review that focuses on continuing research about the emergence of German economic power after the fall of the Soviet Union. By Publication Order your sources by publication chronology, then, only if the order demonstrates a more important trend. For instance, you could order a review of literature on environmental studies of brown fields if the progression revealed, for example, a change in the soil collection practices of the researchers who wrote and/or conducted the studies. Thematic [“conceptual categories”] A thematic literature review is the most common approach to summarizing prior research in the social and behavioral sciences. Thematic reviews are organized around a topic or issue, rather than the progression of time, although the progression of time may still be incorporated into a thematic review. For example, a review of the Internet’s impact on American presidential politics could focus on the development of online political satire. While the study focuses on one topic, the Internet’s impact on American presidential politics, it would still be organized chronologically reflecting technological developments in media. The difference in this example between a "chronological" and a "thematic" approach is what is emphasized the most: themes related to the role of the Internet in presidential politics. Note that more authentic thematic reviews tend to break away from chronological order. A review organized in this manner would shift between time periods within each section according to the point being made. Methodological A methodological approach focuses on the methods utilized by the researcher. For the Internet in American presidential politics project, one methodological approach would be to look at cultural differences between the portrayal of American presidents on American, British, and French websites. Or the review might focus on the fundraising impact of the Internet on a particular political party. A methodological scope will influence either the types of documents in the review or the way in which these documents are discussed.

Other Sections of Your Literature Review Once you've decided on the organizational method for your literature review, the sections you need to include in the paper should be easy to figure out because they arise from your organizational strategy. In other words, a chronological review would have subsections for each vital time period; a thematic review would have subtopics based upon factors that relate to the theme or issue. However, sometimes you may need to add additional sections that are necessary for your study, but do not fit in the organizational strategy of the body. What other sections you include in the body is up to you. However, only include what is necessary for the reader to locate your study within the larger scholarship about the research problem.

Here are examples of other sections, usually in the form of a single paragraph, you may need to include depending on the type of review you write:

• Current Situation : Information necessary to understand the current topic or focus of the literature review.
• Sources Used : Describes the methods and resources [e.g., databases] you used to identify the literature you reviewed.
• History : The chronological progression of the field, the research literature, or an idea that is necessary to understand the literature review, if the body of the literature review is not already a chronology.
• Selection Methods : Criteria you used to select (and perhaps exclude) sources in your literature review. For instance, you might explain that your review includes only peer-reviewed [i.e., scholarly] sources.
• Standards : Description of the way in which you present your information.
• Questions for Further Research : What questions about the field has the review sparked? How will you further your research as a result of the review?

IV.  Writing Your Literature Review

Once you've settled on how to organize your literature review, you're ready to write each section. When writing your review, keep in mind these issues.

Use Evidence A literature review section is, in this sense, just like any other academic research paper. Your interpretation of the available sources must be backed up with evidence [citations] that demonstrates that what you are saying is valid. Be Selective Select only the most important points in each source to highlight in the review. The type of information you choose to mention should relate directly to the research problem, whether it is thematic, methodological, or chronological. Related items that provide additional information, but that are not key to understanding the research problem, can be included in a list of further readings . Use Quotes Sparingly Some short quotes are appropriate if you want to emphasize a point, or if what an author stated cannot be easily paraphrased. Sometimes you may need to quote certain terminology that was coined by the author, is not common knowledge, or taken directly from the study. Do not use extensive quotes as a substitute for using your own words in reviewing the literature. Summarize and Synthesize Remember to summarize and synthesize your sources within each thematic paragraph as well as throughout the review. Recapitulate important features of a research study, but then synthesize it by rephrasing the study's significance and relating it to your own work and the work of others. Keep Your Own Voice While the literature review presents others' ideas, your voice [the writer's] should remain front and center. For example, weave references to other sources into what you are writing but maintain your own voice by starting and ending the paragraph with your own ideas and wording. Use Caution When Paraphrasing When paraphrasing a source that is not your own, be sure to represent the author's information or opinions accurately and in your own words. Even when paraphrasing an author’s work, you still must provide a citation to that work.

V.  Common Mistakes to Avoid

These are the most common mistakes made in reviewing social science research literature.

• Sources in your literature review do not clearly relate to the research problem;
• You do not take sufficient time to define and identify the most relevant sources to use in the literature review related to the research problem;
• Relies exclusively on secondary analytical sources rather than including relevant primary research studies or data;
• Uncritically accepts another researcher's findings and interpretations as valid, rather than examining critically all aspects of the research design and analysis;
• Does not describe the search procedures that were used in identifying the literature to review;
• Reports isolated statistical results rather than synthesizing them in chi-squared or meta-analytic methods; and,
• Only includes research that validates assumptions and does not consider contrary findings and alternative interpretations found in the literature.

Cook, Kathleen E. and Elise Murowchick. “Do Literature Review Skills Transfer from One Course to Another?” Psychology Learning and Teaching 13 (March 2014): 3-11; Fink, Arlene. Conducting Research Literature Reviews: From the Internet to Paper . 2nd ed. Thousand Oaks, CA: Sage, 2005; Hart, Chris. Doing a Literature Review: Releasing the Social Science Research Imagination . Thousand Oaks, CA: Sage Publications, 1998; Jesson, Jill. Doing Your Literature Review: Traditional and Systematic Techniques . London: SAGE, 2011; Literature Review Handout. Online Writing Center. Liberty University; Literature Reviews. The Writing Center. University of North Carolina; Onwuegbuzie, Anthony J. and Rebecca Frels. Seven Steps to a Comprehensive Literature Review: A Multimodal and Cultural Approach . Los Angeles, CA: SAGE, 2016; Ridley, Diana. The Literature Review: A Step-by-Step Guide for Students . 2nd ed. Los Angeles, CA: SAGE, 2012; Randolph, Justus J. “A Guide to Writing the Dissertation Literature Review." Practical Assessment, Research, and Evaluation. vol. 14, June 2009; Sutton, Anthea. Systematic Approaches to a Successful Literature Review . Los Angeles, CA: Sage Publications, 2016; Taylor, Dena. The Literature Review: A Few Tips On Conducting It. University College Writing Centre. University of Toronto; Writing a Literature Review. Academic Skills Centre. University of Canberra.

Writing Tip

Break Out of Your Disciplinary Box!

Thinking interdisciplinarily about a research problem can be a rewarding exercise in applying new ideas, theories, or concepts to an old problem. For example, what might cultural anthropologists say about the continuing conflict in the Middle East? In what ways might geographers view the need for better distribution of social service agencies in large cities than how social workers might study the issue? You don’t want to substitute a thorough review of core research literature in your discipline for studies conducted in other fields of study. However, particularly in the social sciences, thinking about research problems from multiple vectors is a key strategy for finding new solutions to a problem or gaining a new perspective. Consult with a librarian about identifying research databases in other disciplines; almost every field of study has at least one comprehensive database devoted to indexing its research literature.

Frodeman, Robert. The Oxford Handbook of Interdisciplinarity . New York: Oxford University Press, 2010.

Another Writing Tip

Don't Just Review for Content!

While conducting a review of the literature, maximize the time you devote to writing this part of your paper by thinking broadly about what you should be looking for and evaluating. Review not just what scholars are saying, but how are they saying it. Some questions to ask:

• How are they organizing their ideas?
• What methods have they used to study the problem?
• What theories have been used to explain, predict, or understand their research problem?
• What sources have they cited to support their conclusions?
• How have they used non-textual elements [e.g., charts, graphs, figures, etc.] to illustrate key points?

When you begin to write your literature review section, you'll be glad you dug deeper into how the research was designed and constructed because it establishes a means for developing more substantial analysis and interpretation of the research problem.

Hart, Chris. Doing a Literature Review: Releasing the Social Science Research Imagination . Thousand Oaks, CA: Sage Publications, 1 998.

Yet Another Writing Tip

When Do I Know I Can Stop Looking and Move On?

Here are several strategies you can utilize to assess whether you've thoroughly reviewed the literature:

• Look for repeating patterns in the research findings . If the same thing is being said, just by different people, then this likely demonstrates that the research problem has hit a conceptual dead end. At this point consider: Does your study extend current research?  Does it forge a new path? Or, does is merely add more of the same thing being said?
• Look at sources the authors cite to in their work . If you begin to see the same researchers cited again and again, then this is often an indication that no new ideas have been generated to address the research problem.
• Search Google Scholar to identify who has subsequently cited leading scholars already identified in your literature review [see next sub-tab]. This is called citation tracking and there are a number of sources that can help you identify who has cited whom, particularly scholars from outside of your discipline. Here again, if the same authors are being cited again and again, this may indicate no new literature has been written on the topic.

Onwuegbuzie, Anthony J. and Rebecca Frels. Seven Steps to a Comprehensive Literature Review: A Multimodal and Cultural Approach . Los Angeles, CA: Sage, 2016; Sutton, Anthea. Systematic Approaches to a Successful Literature Review . Los Angeles, CA: Sage Publications, 2016.

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Literature Review: Lit Review Sources

• Lit Review Types
• GRADE System
• Do a Lit Review
• Citation Justice
• Lit Review Sources
• AI for Research This link opens in a new window

Where do I find information for a literature review?

Research is done by...

...by way of...

...communicated through...

...and organized in...

Types of sources for a review...

• Primary source: Usually a report by the original researchers of a study (unfiltered sources)
• Secondary source: Description or summary by somebody other than the original researcher, e.g. a review article (filtered sources)
• Conceptual/theoretical: Papers concerned with description or analysis of theories or concepts associated with the topic
• Anecdotal/opinion/clinical: Views or opinions about the subject that are not research, review or theoretical (case studies or reports from clinical settings)

A Heirarchy of research information:

Source: SUNY Downstate Medical Center. Medical Research Library of Brooklyn. Evidence Based Medicine Course. A Guide to Research Methods: The Evidence Pyramid: http://library.downstate.edu/EBM2/2100.htm

Life Cycle of Publication

Click image to enlarge

Scientific information has a ‘life cycle’ of its own… it is born as an idea, and then matures and becomes more available to the public. First it appears within the so-called ‘invisible college’ of experts in the field, discussed at conferences and symposia or posted as pre-prints for comments and corrections. Then it appears in the published literature (the primary literature), often as a journal article in a peer-reviewed journal.

Researchers can use the indexing and alerting services of the secondary literature to find out what has been published in a field. Depending on how much information is added by the indexer or abstracter, this may take a few months (though electronic publication has sped up this process). Finally, the information may appear in more popular or reference sources, sometimes called the tertiary literature.

The person beginning a literature search may take this process in reverse: using tertiary sources for general background, then going to the secondary literature to survey what has been published, following up by finding the original (primary) sources, and generating their own research Idea.

(Original content by Wade Lee-Smith)

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How to Write a Literature Review: Primary and Secondary Sources

• Writing a Literature Review in APA Format
• Chicago/Turabian Citation Style
• Primary and Secondary Sources
• Basic Research Strategies
• Evaluating Sources
• Using the Library's Ebooks
• Using the Library's Catalog
• Copyright Information
• Contact Information & Feedback

Primary versus Secondary Sources

Primary vs. secondary videos.

Primary, Secondary, & Tertiary Sources The content of research papers may come from different types of sources, such as:

• Your own opinion and analysis
• Primary sources
• Secondary sources
• Tertiary sources

It may not be necessary to include each of these types of sources in every paper you write, but your instructor may require you to include them. It is important to understand the characteristics of primary, secondary and tertiary sources–they each serve a different purpose throughout the research process, and can strengthen your assignment, too.

It can be difficult to figure out if a source is considered primary, secondary, or tertiary. We will explain the differences and provide examples of each in this tutorial. If you are still not sure if a source you would like to use is primary, secondary, or tertiary, ask a librarian or teacher.

What is a Primary Source? Primary sources are first-hand, authoritative accounts of an event, topic, or historical time period. They are typically produced at the time of the event by a person who experienced it, but can also be made later on in the form of personal memoirs or oral histories.

Anything that contains original information on a topic is considered a primary source. Usually, primary sources are the object discussed in your paper. For instance, if you are writing an analysis on Upton Sinclair’s The Jungle, the book would be a primary source. But, just because a source is old does not mean it is a primary source.

Some examples of original, first-hand, authoritative accounts include:

• Letters, diaries or journals (Personal thoughts)
• Original photographs
• First-hand newspaper reports
• Speeches, autobiographies
• Creative works like plays, paintings and songs
• Research data and surveys

What is a Secondary Source? Secondary sources interpret or critique primary sources. They often include an analysis of the event that was discussed or featured in the primary source.  They are second-hand accounts that interpret or draw conclusions from one or more primary sources.

Some examples of works that interpret or critique primary sources include:

• Textbooks (May also be considered tertiary)
• Essays or reviews
• Articles that analyze or discuss ideas and events
• Criticisms or commentaries

What is a Tertiary Source? Tertiary sources generally provide an overview or summary of a topic, and may contain both primary and secondary sources. The information is displayed as entirely factual, and does not include analysis or critique.  Tertiary sources can also be collections of primary and secondary sources, such as databases, bibliographies and directories.

Some examples of sources that provide a summary or collection of a topic include:

• Textbooks (May also be considered secondary)
• Bibliographies or abstracts
• Wikipedia articles
• Encyclopedias

Using Primary, secondary and Tertiary Sources in Research Let’s say you are writing a research paper on the Equal Rights Amendment (ERA) of 1972, but you are unfamiliar with it. A good place to gather a general idea or understanding of the ERA would be a tertiary source, such as Wikipedia or the Encyclopedia Britannica. There, you can read a summary of events on its history, key people involved, and legislation.

To find more in-depth analysis on the Equal Rights Amendment, you consult a secondary source: the nonfiction book Why We Lost the ERA by Jane Mansbridge and a newspaper article from the 1970’s that discuss and review the legislation. These provide a more focused analysis of the Equal Rights Amendment that you can include as sources in your paper (make sure you cite them!).  A primary source that could bolster your research would be a government document detailing the ERA legislation that initially passed in Congress, giving a first-hand account of the legislation that went through the House and Senate in 1972.

This video provides a great overview of primary and secondary sources: [ youtube http://www.youtube.com/watch?v= PgfQC4d3pKc &w=420&h=315]

Source:  http://content.easybib.com/students/research-guide/primary-secondary-tertiary-sources/

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Literature review sources

Sources for literature review can be divided into three categories as illustrated in table below. In your dissertation you will need to use all three categories of literature review sources:

Sources for literature review and examples

Generally, your literature review should integrate a wide range of sources such as:

• Books . Textbooks remain as the most important source to find models and theories related to the research area. Research the most respected authorities in your selected research area and find the latest editions of books authored by them. For example, in the area of marketing the most notable authors include Philip Kotler, Seth Godin, Malcolm Gladwell, Emanuel Rosen and others.
• Magazines . Industry-specific magazines are usually rich in scholarly articles and they can be effective source to learn about the latest trends and developments in the research area. Reading industry magazines can be the most enjoyable part of the literature review, assuming that your selected research area represents an area of your personal and professional interests, which should be the case anyways.
• Newspapers can be referred to as the main source of up-to-date news about the latest events related to the research area. However, the proportion of the use of newspapers in literature review is recommended to be less compared to alternative sources of secondary data such as books and magazines. This is due to the fact that newspaper articles mainly lack depth of analyses and discussions.
• Online articles . You can find online versions of all of the above sources. However, note that the levels of reliability of online articles can be highly compromised depending on the source due to the high levels of ease with which articles can be published online. Opinions offered in a wide range of online discussion blogs cannot be usually used in literature review. Similarly, dissertation assessors are not keen to appreciate references to a wide range of blogs, unless articles in these blogs are authored by respected authorities in the research area.

Your secondary data sources may comprise certain amount of grey literature as well. The term grey literature refers to type of literature produced by government, academics, business and industry in print and electronic formats, which is not controlled by commercial publishers. It is called ‘grey’ because the status of the information in grey literature is not certain. In other words, any publication that has not been peer reviewed for publication is grey literature.

The necessity to use grey literature arises when there is no enough peer reviewed publications are available for the subject of your study.

John Dudovskiy

Conducting a Literature Review: Types of Literature

• Introduction
• 1. Choose Your Topic

Types of Literature

• 3. Search the Literature
• 4. Read & Analyze the Literature
• 5. Write the Review
• Keeping Track of Information
• Style Guides

Different types of publications have different characteristics.

Primary Literature Primary sources means original studies, based on direct observation, use of statistical records, interviews, or experimental methods, of actual practices or the actual impact of practices or policies. They are authored by researchers, contains original research data, and are usually published in a peer-reviewed journal. Primary literature may also include conference papers, pre-prints, or preliminary reports. Also called empirical research .

Secondary Literature Secondary literature consists of interpretations and evaluations that are derived from or refer to the primary source literature. Examples include review articles (such as meta-analysis and systematic reviews) and reference works. Professionals within each discipline take the primary literature and synthesize, generalize, and integrate new research.

Tertiary Literature Tertiary literature consists of a distillation and collection of primary and secondary sources such as textbooks, encyclopedia articles, and guidebooks or handbooks. The purpose of tertiary literature is to provide an overview of key research findings and an introduction to principles and practices within the discipline.

Adapted from the Information Services Department of the Library of the Health Sciences-Chicago , University of Illinois at Chicago.

Types of Scientific Publications

These examples and descriptions of publication types will give you an idea of how to use various works and why you would want to write a particular kind of paper.

• Scholarly article aka empirical article
• Review article
• Conference paper

Scholarly (aka empirical) article -- example

Empirical studies use data derived from observation or experiment. Original research papers (also called primary research articles) that describe empirical studies and their results are published in academic journals.  Articles that report empirical research contain different sections which relate to the steps of the scientific method.

      Abstract - The abstract provides a very brief summary of the research.

     Introduction - The introduction sets the research in a context, which provides a review of related research and develops the hypotheses for the research.

     Method - The method section describes how the research was conducted.

     Results - The results section describes the outcomes of the study.

     Discussion - The discussion section contains the interpretations and implications of the study.

     References - A references section lists the articles, books, and other material cited in the report.

Review article -- example

A review article summarizes a particular field of study and places the recent research in context. It provides an overview and is an excellent introduction to a subject area. The references used in a review article are helpful as they lead to more in-depth research.

Many databases have limits or filters to search for review articles. You can also search by keywords like review article, survey, overview, summary, etc.

Conference proceedings, abstracts and reports -- example

Conference proceedings, abstracts and reports are not usually peer-reviewed.  A conference article is similar to a scholarly article insofar as it is academic. Conference articles are published much more quickly than scholarly articles. You can find conference papers in many of the same places as scholarly articles.

How Do You Identify Empirical Articles?

To identify an article based on empirical research, look for the following characteristics:

     The article is published in a peer-reviewed journal .

     The article includes charts, graphs, or statistical analysis .

     The article is substantial in size , likely to be more than 5 pages long.

     The article contains the following parts (the exact terms may vary): abstract, introduction, method, results, discussion, references .

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Primary Sources: What are Primary Sources?

• Primary Sources Online
• How to Find Primary Sources
• How to Work w/ Primary Sources
• What are Primary Sources?

What are primary sources?

What constitutes a primary source varies by discipline.

In the social sciences the terms primary literature and primary data are preferred over primary source . The former imply the results of original research or experimentation, usually gathered in the field and later reported in the peer-reviewed journal literature. Disciplinary examples are too numerous to list but include anthropologists who undertake dirt archaeology and ethnographic fieldwork; education researchers who gather data in the classroom; linguists who record communication patterns in a particular language community; and political scientists who conduct voter polls and surveys. In many social sciences disciplines a fine-grained distinction is made between the primary literature (i.e., the scholarly articles and presentations that report on original research) and the primary data (i.e., the "raw" data collected by researchers through interviews, observations, and survey instruments).

In the arts and humanities primary sources are original, creative works. These include photographs, paintings, prints, sculptures, ceramics, textiles and other studio works; original literary creations such as novels, plays, short stories, and poems; musical compositions and performances; and in architecture buildings, complexes, and even whole cities. Art historians greatly prefer, when possible, to study original artworks yet often make do with re-productions. An art historian studying Olmec sculpture, for instance, might work with high-quality illustrations published in an exhibition catalog or found in library databases such as ARTstor. Preferred would be to study Olmec sculptures at the museum. Best of all might be the opportunity to study the sculptures in situ . The latter could be logistically difficult or even impossible if the original archaeological context has been lost.

In history primary sources are "original records created at the time historical events occurred or well after events in the form of memoirs and oral histories. Primary sources may include letters, manuscripts, diaries, journals, newspapers, speeches, interviews, memoirs, documents produced by government agencies such as Congress or the Office of the President, photographs, audio recordings, moving pictures or video recordings, research data [social scientists' primary data, described above], and objects or artifacts such as works of art or ancient roads, buildings, tools, and weapons. These sources serve as the raw material to interpret the past..." ( Primary Sources on the Web , a website of the History Section of RUSA, American Library Association). Primary sources are available in archives or as re-productions of originals published online or in books widely held by academic libraries.

What are secondary sources?

What constitutes a secondary source is dependent on the discipline but the difference is largely semantic.

In the social sciences a secondary source is based on or written about the primary literature . A secondary source analyzes, editorializes, reports on, or summarizes the primary literature. While secondary sources in the social sciences are sometimes scholarly (e.g., a scholarly book that summarizes a body of primary literature or a review article published in an academic journal), more typically secondary sources in the social sciences appear in credible but popular publications. Examples include general-interest magazines such as Newsweek and Time , highbrow publications such as The Atlantic and New Yorker , newspapers such as The New York Times , and books and websites aimed at non-specialized audiences. The "conversation" social scientists have with one another occurs not in these popular publications but rather within the primary literature .

In the arts , humanities , and history a secondary source is also based on or written about primary sources . A secondary source in the humanities, however, is typically if not always scholarly (e.g., a book aimed at other scholars or an article published in a peer-reviewed journal). Historians, for instance, explore the significance of Thomas Jefferson's writings (i.e., the primary sources) in scholarly books and peer-reviewed journal articles written by and for other scholars .

Scholars in all disciplines work to address unresolved disciplinary problems and questions. At the same time, scholars strive to complicate what is already known. In all cases such "conversations" nearly always occur within the pages of scholarly books (i.e., monographs and edited volumes), and in peer-reviewed journal articles. Students will typically cite these sources in research papers.

What are tertiary sources?

You might encounter a tertiary source, more commonly called a reference work. Two layers removed from the primary evidence, tertiary sources are based on secondary sources. They contextualize or summarize secondary sources or list, index, or in some other way promote their efficient discovery. Reference works provide researchers with the information needed to conduct further research. Types of reference works include bibliographies, biographies, catalogs, chronologies, companions, dictionaries, directories, encyclopedias, handbooks, and indexes.

Scholars do more than present what is already known. Academics from undergraduates to senior scholars develop cogent arguments in support of their theses. The baseline information contained in encyclopedia articles cannot substitute for original scholarship. This is one reason why reference works are not generally cited in scholars' own bibliographies or reference lists. And yet each type or class of information—primary, secondary, and tertiary—fulfills a critical function in the research process.

Questions about what constitutes or how to find primary sources for your project? Please contact me for help!  

David C. Murray Humanities Librarian [email protected] 609-771-3217

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Ten Simple Rules for Writing a Literature Review

Marco pautasso.

1 Centre for Functional and Evolutionary Ecology (CEFE), CNRS, Montpellier, France

2 Centre for Biodiversity Synthesis and Analysis (CESAB), FRB, Aix-en-Provence, France

Literature reviews are in great demand in most scientific fields. Their need stems from the ever-increasing output of scientific publications [1] . For example, compared to 1991, in 2008 three, eight, and forty times more papers were indexed in Web of Science on malaria, obesity, and biodiversity, respectively [2] . Given such mountains of papers, scientists cannot be expected to examine in detail every single new paper relevant to their interests [3] . Thus, it is both advantageous and necessary to rely on regular summaries of the recent literature. Although recognition for scientists mainly comes from primary research, timely literature reviews can lead to new synthetic insights and are often widely read [4] . For such summaries to be useful, however, they need to be compiled in a professional way [5] .

When starting from scratch, reviewing the literature can require a titanic amount of work. That is why researchers who have spent their career working on a certain research issue are in a perfect position to review that literature. Some graduate schools are now offering courses in reviewing the literature, given that most research students start their project by producing an overview of what has already been done on their research issue [6] . However, it is likely that most scientists have not thought in detail about how to approach and carry out a literature review.

Reviewing the literature requires the ability to juggle multiple tasks, from finding and evaluating relevant material to synthesising information from various sources, from critical thinking to paraphrasing, evaluating, and citation skills [7] . In this contribution, I share ten simple rules I learned working on about 25 literature reviews as a PhD and postdoctoral student. Ideas and insights also come from discussions with coauthors and colleagues, as well as feedback from reviewers and editors.

Rule 1: Define a Topic and Audience

How to choose which topic to review? There are so many issues in contemporary science that you could spend a lifetime of attending conferences and reading the literature just pondering what to review. On the one hand, if you take several years to choose, several other people may have had the same idea in the meantime. On the other hand, only a well-considered topic is likely to lead to a brilliant literature review [8] . The topic must at least be:

• interesting to you (ideally, you should have come across a series of recent papers related to your line of work that call for a critical summary),
• an important aspect of the field (so that many readers will be interested in the review and there will be enough material to write it), and
• a well-defined issue (otherwise you could potentially include thousands of publications, which would make the review unhelpful).

Ideas for potential reviews may come from papers providing lists of key research questions to be answered [9] , but also from serendipitous moments during desultory reading and discussions. In addition to choosing your topic, you should also select a target audience. In many cases, the topic (e.g., web services in computational biology) will automatically define an audience (e.g., computational biologists), but that same topic may also be of interest to neighbouring fields (e.g., computer science, biology, etc.).

Rule 2: Search and Re-search the Literature

After having chosen your topic and audience, start by checking the literature and downloading relevant papers. Five pieces of advice here:

• keep track of the search items you use (so that your search can be replicated [10] ),
• keep a list of papers whose pdfs you cannot access immediately (so as to retrieve them later with alternative strategies),
• use a paper management system (e.g., Mendeley, Papers, Qiqqa, Sente),
• define early in the process some criteria for exclusion of irrelevant papers (these criteria can then be described in the review to help define its scope), and
• do not just look for research papers in the area you wish to review, but also seek previous reviews.

The chances are high that someone will already have published a literature review ( Figure 1 ), if not exactly on the issue you are planning to tackle, at least on a related topic. If there are already a few or several reviews of the literature on your issue, my advice is not to give up, but to carry on with your own literature review,

The bottom-right situation (many literature reviews but few research papers) is not just a theoretical situation; it applies, for example, to the study of the impacts of climate change on plant diseases, where there appear to be more literature reviews than research studies [33] .

• discussing in your review the approaches, limitations, and conclusions of past reviews,
• trying to find a new angle that has not been covered adequately in the previous reviews, and
• incorporating new material that has inevitably accumulated since their appearance.

When searching the literature for pertinent papers and reviews, the usual rules apply:

• be thorough,
• use different keywords and database sources (e.g., DBLP, Google Scholar, ISI Proceedings, JSTOR Search, Medline, Scopus, Web of Science), and
• look at who has cited past relevant papers and book chapters.

Rule 3: Take Notes While Reading

If you read the papers first, and only afterwards start writing the review, you will need a very good memory to remember who wrote what, and what your impressions and associations were while reading each single paper. My advice is, while reading, to start writing down interesting pieces of information, insights about how to organize the review, and thoughts on what to write. This way, by the time you have read the literature you selected, you will already have a rough draft of the review.

Of course, this draft will still need much rewriting, restructuring, and rethinking to obtain a text with a coherent argument [11] , but you will have avoided the danger posed by staring at a blank document. Be careful when taking notes to use quotation marks if you are provisionally copying verbatim from the literature. It is advisable then to reformulate such quotes with your own words in the final draft. It is important to be careful in noting the references already at this stage, so as to avoid misattributions. Using referencing software from the very beginning of your endeavour will save you time.

Rule 4: Choose the Type of Review You Wish to Write

After having taken notes while reading the literature, you will have a rough idea of the amount of material available for the review. This is probably a good time to decide whether to go for a mini- or a full review. Some journals are now favouring the publication of rather short reviews focusing on the last few years, with a limit on the number of words and citations. A mini-review is not necessarily a minor review: it may well attract more attention from busy readers, although it will inevitably simplify some issues and leave out some relevant material due to space limitations. A full review will have the advantage of more freedom to cover in detail the complexities of a particular scientific development, but may then be left in the pile of the very important papers “to be read” by readers with little time to spare for major monographs.

There is probably a continuum between mini- and full reviews. The same point applies to the dichotomy of descriptive vs. integrative reviews. While descriptive reviews focus on the methodology, findings, and interpretation of each reviewed study, integrative reviews attempt to find common ideas and concepts from the reviewed material [12] . A similar distinction exists between narrative and systematic reviews: while narrative reviews are qualitative, systematic reviews attempt to test a hypothesis based on the published evidence, which is gathered using a predefined protocol to reduce bias [13] , [14] . When systematic reviews analyse quantitative results in a quantitative way, they become meta-analyses. The choice between different review types will have to be made on a case-by-case basis, depending not just on the nature of the material found and the preferences of the target journal(s), but also on the time available to write the review and the number of coauthors [15] .

Rule 5: Keep the Review Focused, but Make It of Broad Interest

Whether your plan is to write a mini- or a full review, it is good advice to keep it focused 16 , 17 . Including material just for the sake of it can easily lead to reviews that are trying to do too many things at once. The need to keep a review focused can be problematic for interdisciplinary reviews, where the aim is to bridge the gap between fields [18] . If you are writing a review on, for example, how epidemiological approaches are used in modelling the spread of ideas, you may be inclined to include material from both parent fields, epidemiology and the study of cultural diffusion. This may be necessary to some extent, but in this case a focused review would only deal in detail with those studies at the interface between epidemiology and the spread of ideas.

While focus is an important feature of a successful review, this requirement has to be balanced with the need to make the review relevant to a broad audience. This square may be circled by discussing the wider implications of the reviewed topic for other disciplines.

Rule 6: Be Critical and Consistent

Reviewing the literature is not stamp collecting. A good review does not just summarize the literature, but discusses it critically, identifies methodological problems, and points out research gaps [19] . After having read a review of the literature, a reader should have a rough idea of:

• the major achievements in the reviewed field,
• the main areas of debate, and
• the outstanding research questions.

It is challenging to achieve a successful review on all these fronts. A solution can be to involve a set of complementary coauthors: some people are excellent at mapping what has been achieved, some others are very good at identifying dark clouds on the horizon, and some have instead a knack at predicting where solutions are going to come from. If your journal club has exactly this sort of team, then you should definitely write a review of the literature! In addition to critical thinking, a literature review needs consistency, for example in the choice of passive vs. active voice and present vs. past tense.

Rule 7: Find a Logical Structure

Like a well-baked cake, a good review has a number of telling features: it is worth the reader's time, timely, systematic, well written, focused, and critical. It also needs a good structure. With reviews, the usual subdivision of research papers into introduction, methods, results, and discussion does not work or is rarely used. However, a general introduction of the context and, toward the end, a recapitulation of the main points covered and take-home messages make sense also in the case of reviews. For systematic reviews, there is a trend towards including information about how the literature was searched (database, keywords, time limits) [20] .

How can you organize the flow of the main body of the review so that the reader will be drawn into and guided through it? It is generally helpful to draw a conceptual scheme of the review, e.g., with mind-mapping techniques. Such diagrams can help recognize a logical way to order and link the various sections of a review [21] . This is the case not just at the writing stage, but also for readers if the diagram is included in the review as a figure. A careful selection of diagrams and figures relevant to the reviewed topic can be very helpful to structure the text too [22] .

Rule 8: Make Use of Feedback

Reviews of the literature are normally peer-reviewed in the same way as research papers, and rightly so [23] . As a rule, incorporating feedback from reviewers greatly helps improve a review draft. Having read the review with a fresh mind, reviewers may spot inaccuracies, inconsistencies, and ambiguities that had not been noticed by the writers due to rereading the typescript too many times. It is however advisable to reread the draft one more time before submission, as a last-minute correction of typos, leaps, and muddled sentences may enable the reviewers to focus on providing advice on the content rather than the form.

Feedback is vital to writing a good review, and should be sought from a variety of colleagues, so as to obtain a diversity of views on the draft. This may lead in some cases to conflicting views on the merits of the paper, and on how to improve it, but such a situation is better than the absence of feedback. A diversity of feedback perspectives on a literature review can help identify where the consensus view stands in the landscape of the current scientific understanding of an issue [24] .

Rule 9: Include Your Own Relevant Research, but Be Objective

In many cases, reviewers of the literature will have published studies relevant to the review they are writing. This could create a conflict of interest: how can reviewers report objectively on their own work [25] ? Some scientists may be overly enthusiastic about what they have published, and thus risk giving too much importance to their own findings in the review. However, bias could also occur in the other direction: some scientists may be unduly dismissive of their own achievements, so that they will tend to downplay their contribution (if any) to a field when reviewing it.

In general, a review of the literature should neither be a public relations brochure nor an exercise in competitive self-denial. If a reviewer is up to the job of producing a well-organized and methodical review, which flows well and provides a service to the readership, then it should be possible to be objective in reviewing one's own relevant findings. In reviews written by multiple authors, this may be achieved by assigning the review of the results of a coauthor to different coauthors.

Rule 10: Be Up-to-Date, but Do Not Forget Older Studies

Given the progressive acceleration in the publication of scientific papers, today's reviews of the literature need awareness not just of the overall direction and achievements of a field of inquiry, but also of the latest studies, so as not to become out-of-date before they have been published. Ideally, a literature review should not identify as a major research gap an issue that has just been addressed in a series of papers in press (the same applies, of course, to older, overlooked studies (“sleeping beauties” [26] )). This implies that literature reviewers would do well to keep an eye on electronic lists of papers in press, given that it can take months before these appear in scientific databases. Some reviews declare that they have scanned the literature up to a certain point in time, but given that peer review can be a rather lengthy process, a full search for newly appeared literature at the revision stage may be worthwhile. Assessing the contribution of papers that have just appeared is particularly challenging, because there is little perspective with which to gauge their significance and impact on further research and society.

Inevitably, new papers on the reviewed topic (including independently written literature reviews) will appear from all quarters after the review has been published, so that there may soon be the need for an updated review. But this is the nature of science [27] – [32] . I wish everybody good luck with writing a review of the literature.

Acknowledgments

Many thanks to M. Barbosa, K. Dehnen-Schmutz, T. Döring, D. Fontaneto, M. Garbelotto, O. Holdenrieder, M. Jeger, D. Lonsdale, A. MacLeod, P. Mills, M. Moslonka-Lefebvre, G. Stancanelli, P. Weisberg, and X. Xu for insights and discussions, and to P. Bourne, T. Matoni, and D. Smith for helpful comments on a previous draft.

Funding Statement

This work was funded by the French Foundation for Research on Biodiversity (FRB) through its Centre for Synthesis and Analysis of Biodiversity data (CESAB), as part of the NETSEED research project. The funders had no role in the preparation of the manuscript.

Primary Sources - Literature: Home

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Finding Primary Sources

Primary sources in literature are original, uninterpreted information (often, but not exclusively textual) relevant to a literary research topic. Examples include original works of fiction, art, or music; letters; diaries; interviews; or even works of criticism.

The key question to ask when trying to classify a source as primary versus secondary is how you intend to use it . If a work was written or created during the time period that you are researching, it can be used as a primary source.

For example:

A 1922 review of T. S. Eliot's The Waste Land would be considered a secondary source if your project is an analysis of Eliot's poem, but would be a primary source if your topic is the critical reception of Eliot's works, or the perception of modernism as a literary style in the 1920s.

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Literature Reviews: Types of Literature

• Library Basics
• 1. Choose Your Topic
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• Types of Clinical Study Designs

Types of Literature

• 3. Search the Literature
• 4. Read & Analyze the Literature
• 5. Write the Review
• Keeping Track of Information
• Style Guides
• Books, Tutorials & Examples

Different types of publications have different characteristics.

Primary Literature Primary sources means original studies, based on direct observation, use of statistical records, interviews, or experimental methods, of actual practices or the actual impact of practices or policies. They are authored by researchers, contains original research data, and are usually published in a peer-reviewed journal. Primary literature may also include conference papers, pre-prints, or preliminary reports. Also called empirical research .

Secondary Literature Secondary literature consists of interpretations and evaluations that are derived from or refer to the primary source literature. Examples include review articles (such as meta-analysis and systematic reviews) and reference works. Professionals within each discipline take the primary literature and synthesize, generalize, and integrate new research.

Tertiary Literature Tertiary literature consists of a distillation and collection of primary and secondary sources such as textbooks, encyclopedia articles, and guidebooks or handbooks. The purpose of tertiary literature is to provide an overview of key research findings and an introduction to principles and practices within the discipline.

Adapted from the Information Services Department of the Library of the Health Sciences-Chicago , University of Illinois at Chicago.

Types of Scientific Publications

These examples and descriptions of publication types will give you an idea of how to use various works and why you would want to write a particular kind of paper.

• Scholarly article aka empirical article
• Review article
• Conference paper

Scholarly (aka empirical) article -- example

Empirical studies use data derived from observation or experiment. Original research papers (also called primary research articles) that describe empirical studies and their results are published in academic journals.  Articles that report empirical research contain different sections which relate to the steps of the scientific method.

      Abstract - The abstract provides a very brief summary of the research.

     Introduction - The introduction sets the research in a context, which provides a review of related research and develops the hypotheses for the research.

     Method - The method section describes how the research was conducted.

     Results - The results section describes the outcomes of the study.

     Discussion - The discussion section contains the interpretations and implications of the study.

     References - A references section lists the articles, books, and other material cited in the report.

Review article -- example

A review article summarizes a particular field of study and places the recent research in context. It provides an overview and is an excellent introduction to a subject area. The references used in a review article are helpful as they lead to more in-depth research.

Many databases have limits or filters to search for review articles. You can also search by keywords like review article, survey, overview, summary, etc.

Conference proceedings, abstracts and reports -- example

Conference proceedings, abstracts and reports are not usually peer-reviewed.  A conference article is similar to a scholarly article insofar as it is academic. Conference articles are published much more quickly than scholarly articles. You can find conference papers in many of the same places as scholarly articles.

How Do You Identify Empirical Articles?

To identify an article based on empirical research, look for the following characteristics:

     The article is published in a peer-reviewed journal .

     The article includes charts, graphs, or statistical analysis .

     The article is substantial in size , likely to be more than 5 pages long.

     The article contains the following parts (the exact terms may vary): abstract, introduction, method, results, discussion, references .

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Literature Research Guide: Primary Sources

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Primary Sources in Literature

A primary source is "first-hand" information, sources as close as possible to the origin of the information or idea under study.

Primary sources are contrasted with secondary sources, works that provide analysis, commentary, or criticism on the primary source.

In literary studies, primary sources are often creative works, including poems, stories, novels, and so on.

In historical studies, primary sources include written works, recordings, or other source of information from people who were participants or direct witnesses to the events in question.

Examples of commonly used primary sources include government documents, memoirs, personal correspondence, oral histories, and contemporary newspaper accounts.

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Primary Sources: Finding Primary Sources in Literature

• Using Primary Source Material
• Finding Primary Source Material
• Finding Primary Sources in Music
• Finding Primary Resources in History
• Finding Primary Sources in Religion
• Finding Primary Source in Theatre and the Arts
• Finding Primary Sources in Literature

Primary Source Material in Literature

Primary sources of a literary work can include the following:

• Autograph/Holograph ( the author's original manuscript)
• Copies (handwritten by another person: student, professional copyist, monastic scribes)
• First edition
• Early editions ( could be edited by someone close the the author)
• Scholarly editions ( edits made by scholar known for knowledge of author)
• Collected editions ( complete works of author published in scholarly edition - could show variations found in the above sources)

Primary Resources for Literature in the Jerry Falwell Library

• America's Historical Newspapers This link opens in a new window Historic American newspapers providing primary sources for exploring American history, culture, and daily life from 1690 to the early 20th century
• Black Short Fiction and Folklore: African, African American, and Diaspora This link opens in a new window Full-text articles, poems, and short fiction from African authors For more information, view this brief tutorial on using Black Short Fiction and Folklore .
• British Periodicals This link opens in a new window Full-text historical periodicals from the late seventeenth century to the early twentieth on a variety of topics from a British perspective For more information, view this brief tutorial on using British Periodicals .
• Complete Prose of T.S. Eliot: The Critical Edition This link opens in a new window Collected, uncollected, and unpublished essays, reviews, lectures, and commentaries by T. S. Eliot with textual edits, annotations, and cross-references
• EEBO (Early English Books Online) This link opens in a new window Extensive full-text collection of early English books, including titles by John Locke, Captain John Smith, William Shakespeare, and others For more information, view this brief tutorial on using EEBO .
• Emily Dickinson’s Correspondences This link opens in a new window Full-text primary source documents including digital scans of Dickinson’s poems and letters from her correspondence with her sister-in-law Susan Dickinson For more information, view this brief tutorial on using Emily Dickinson’s Correspondences .
• Irish Women Poets of the Romantic Period This link opens in a new window Full-text poems, e-books, and prose from Irish female authors from 1768 to 1842 For more information, view this brief tutorial on using Irish Women Poets .
• Romantic Era Redefined This link opens in a new window Full-text poetry, dramas, and fiction from Britain and North America from 1800 to 1830 For more information, view this brief tutorial on using Romantic Era Redefined .

Online Primary Sources for Literature

• British Library Texts in Context Curated collections of historical materials providing useful contexts for literary works. An excellent starting point for literary research.
• Documenting the American South Documenting the American South (DocSouth) is a digital publishing initiative that provides Internet access to texts, images, and audio files related to southern history, literature, and culture. more... less... Texts, images, and audio files related to southern history, literature, and culture.
• Europeana Search, save and share art, books, films and music from thousands of cultural institutions more... less... Search, save and share art, books, films and music from thousands of cultural institutions
• Google Books Google Books is a service from Google that searches the full text of books and magazines that Google has scanned, converted to text using optical character recognition, and stored in its digital database
• Hathi Trust At HathiTrust, we are stewards of the largest digitized collection of knowledge allowable by copyright law.
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• Part of UN Secretary-General Papers: Ban Ki-moon (2007-2016)
• Part of Perspectives on Terrorism, Vol. 12, No. 4 (August 2018)
• Part of Leveraging Lives: Serbia and Illegal Tunisian Migration to Europe, Carnegie Endowment for International Peace (Mar. 1, 2023)
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Harness the power of visual materials—explore more than 3 million images now on JSTOR.

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Library Research Guide for the History of Science: Introduction

• What is a Primary Source?
• Background and Context/Biography
• Exploring Your Topic
• Using HOLLIS
• What is a Secondary Source?

Page Contents

Knowing a primary source when you see one, kinds of primary sources, find primary sources in hollis, using digital libraries and collections online, using bibliographies.

• Exploring the Special Collections at Harvard
• Citing Sources & Organizing Research

Primary sources provide first-hand testimony or direct evidence concerning a topic under investigation. They are created by witnesses or recorders who experienced the events or conditions being documented.

Often these sources are created at the time when the events or conditions are occurring, but primary sources can also include autobiographies, memoirs, and oral histories recorded later.

Primary sources are characterized by their content, regardless of the format available. (Handwritten notes could be published; the published book might be digitized or put on microfilm, but those notes are still primary sources in any format).

Some types of primary sources:

• Original documents (excerpts or translations acceptable): Diaries, speeches, manuscripts, letters, interviews, news film footage, contemporary newspaper articles, autobiographies, official records, pamphlets, meeting notes, photographs, contemporary sketches
• Creative works : Poetry, drama, novels, music, art 
• Relics or artifacts : Furniture, clothing, buildings

Examples of primary sources include:

• A poster from the Brotherhood of Sleeping Car Porters' 1962 strike
• The papers of William James
• A 1970 U.S. State Dept document updating Nixon on U.S.-Soviet space cooperation activities (Harvard login)
• A British pamphlet: "Electric Lighting for Country Houses," 1898
• Phineas Gage's skull
• The text of J. Robert Oppenheimer's "Atomic Weapons" presentation to the American Philosophical Society

Outline of Primary Sources for History

Archives and Manuscripts

Archives and manuscripts are the unpublished records of persons (letters, notes, diaries, etc.) and organizations. What are Archives?   Usually each archival collection has a (short) catalog record and a detailed finding aid (which is often available online).

• "Catalog record” refers to the kind of record found in library online catalogs, similar to those for books, although often a bit longer. Example of an Archive record .
• “Finding aid” (sometimes called an inventory) generally refers to a list of the folder labels for the collection, accompanied by a brief collection overview (scope and contents note) and a biographical (or institutional) note on the creator of the collection.  Finding aids may be as long as needed given the size of the collection.  They vary considerably according to the practices of individual repositories. Example of a Finding aid .

To find  Archives and manuscripts  at Harvard, go to  HOLLIS Advanced search .  Search your keywords or Subject terms (see the  HOLLIS page of this guide ) in the Library Catalog, limiting to Resource Type: Archives/Manuscripts.  You can choose the library at the right (Search Scope).  Countway  Medicine has abundant medical archives, and Schlesinger has many archives of women activists, many in health and reproductive rights fields.    Sample search on Subject: Women health .

Library Research Guide for Finding Manuscripts and Archival Collections explains

• How to find archives and manuscripts at Harvard
• How to find archives and manuscripts elsewhere in US via search tools and via subject guides .
• How to find archives and manuscripts in Europe and elsewhere.
• Requesting digitization of archival material from Harvard and from other repositories .

For digitized archival material together with other kinds of primary sources:

• Finding Primary Sources Online offers general instructions for finding primary sources online and a list of resources by region and country
• Online Primary Source Collections for the History of Science lists digital collections at Harvard and beyond by topic.
• Online Primary Source Collections for History lists digital collections at Harvard and beyond by topic.

Methods for finding books are described under the HOLLIS page  of this guide and in the Finding Primary Sources in HOLLIS box on this page. 

• Book Reviews may give an indication as to how a scientific work was received. See:   Finding Book Reviews . 
• Numerous, especially pre-1923 books (as well as periodicals and other sources) can be found and full text searched in several digital libraries (see box on this page).

Periodicals

Scientific articles :

Web of Science Citation Indexes (Harvard Login)  (1900- ) articles in all areas of science. Includes medical articles not in PubMed. You can use the Cited Reference search in the Web of Science to find primary source articles that cite a specified article, thus getting an idea of its reception. More information on the Web of Science .

PubMed (1946- ) covers, usually with abstracts, periodical articles on all areas of medicine. - --Be sure to look at the MeSH (Medical Subject Headings)  at the bottom of pertinent records. Very recent articles may not as yet received their MeSH terms.  So look at older records to find the MeSH terms, and use a variety of keywords as well as MeSH terms to find the new records. --​The MeSH terms are the same as the Medical Subject terms found in HOLLIS. --Hit Free article or Try Harvard Library, not the publisher's name to see full text

JSTOR (Harvard Login)  offers full-text of complete runs (up to about 5 years ago) of over 400 journals. JSTOR allows simultaneous or individual searching, full-text searching optional, numerous journals in a variety of fields of science and medicine. See the list at the bottom of the Advanced search screen. JSTOR searches the "Notes and News" sections of journals ( Science is especially rich in this material). In Advanced Search choose Item Type: Miscellaneous to limit largely to "Notes and News".

PsycINFO) (Harvard Login)  (1872- ) indexes the professional and academic literature in psychology and related disciplines

Many more scientific periodical indexes are listed in the Library Research Guide for the History of Science .

General interest magazines and periodicals see:

American Periodicals Series Online (Harvard Login)  (1740-1900) offers full text of about 1100 American periodicals. Includes several scientific and medical journals including the American Journal of Science and the Medical Repository. In cases where a periodical started before 1900, coverage is included until 1940.

British Periodicals (Harvard Login)  (1681-1920) offers full text for several hundred British periodicals.

Ethnic NewsWatch (Harvard Login)  (1959- ) is a full text database of the newspapers, magazines, and journals of the ethnic, minority and native press.

Periodicals Index Online (Harvard Login)  indexes contents of thousands of US and European journals in the humanities and social sciences, from their first issues to 1995.

Reader's Guide Retrospective (WilsonWeb) (Harvard Login)  (1890-1982)  indexes many American popular periodicals.

Many more general periodical indexes are listed in Finding Articles in General and Popular Periodicals (North America and Western Europe) .

Articles in non-science fields (religion, public policy): see the list in the Library Research Guide for History .

Professional/Trade : Aimed at particular trades or professions.  See the Library Research Guide for History

Newspaper articles : see the Guide to Newspapers and Newspaper Indexes .

Personal accounts . These are first person narratives recalling or describing a person’s life and opinions. These include Diaries, memoirs, autobiographies, and when delivered orally and recorded: Oral histories and Interviews.

National Library of Medicine Oral Histories

Regulatory Oral History Hub  (Kenan Institute for Ethics, Duke University) offers links to digital collections containing interviews with regulators, lawyers, and judges. Mainly U.S.

Visual sources :

Records for many, but by no means all, individual Harvard University Library images are available in  HOLLIS Images , an online catalog of images. Records include subjects and a thumbnail image.  HOLLIS Images is included in HOLLIS  searches.

Science & Society Picture Library offers over 50,000 images from the Science Museum (London), the National Museum of Photography, Film & Television and the National Railway Museum.

Database of Scientific Illustrators  (DSI) includes over 12500 illustrators in natural history, medicine, technology and various sciences worldwide, c.1450-1950. Living illustrators excluded. 

NYPL Digital Gallery Pictures of Science: 700 Years of Scientific and Medical Illustration

Images from the History of Medicine (IHM) includes prints and photographs from the U.S. National Library of Medicine. (The IHM is contained within a larger NLM image database, so this link goes to a specialized search).

Images From the History of the Public Health Service: a Photographic Exhibit .

Wellcome Images

Films/Videos

To find films in  HOLLIS , search your topic keywords, then on the right side of the results screen, look at Resource Type and choose video/film.

To find books about films about your topic, search your topic keywords AND "in motion pictures" ​  (in "")

​Film Platform  offers numerous documentary films on a wide variety of subjects.  There are collections on several topics. Searches can be filtered by topic, country of production, and language. 

A list of general sources for images and film is available in the Library Research Guide for History and additional sources for the history of science in Library Research Guide for the History of Science .

Government documents often concern matters of science and health policy.  For Congressional documents, especially committee reports, see ProQuest Congressional (Harvard Login ). 

HathiTrust Digital Library . Each full text item is linked to a standard library catalog record, thus providing good metadata and subject terms. The catalog can be searched separately.  Many government documents are full text viewable.  Search US government department as Author.

More sources are listed in the Library Research Guide for History

For artifacts and other objects , the Historic Scientific Instruments Collection in the Science Center includes over 15,000 instruments, often with contemporary documentation, from 1450 through the 20th century worldwide.

Waywiser, online database of the Collection of Historical Scientific Instruments .

Warren Anatomical Museum of the Center for the History of Medicine in the Countway Library of Medicine has a rich collection of medical artifacts and specimens.

Peabody Museum of Archaeology and Ethnology

Fall 2020: these collections are closed during the pandemic. Check out their links above to see what they have available online.

Primary Source Terms :

You can limit HOLLIS  searches to your time period, but sources may be published later, such as a person's diary published posthumously. Find these with these special Subject terms.

You can use the following terms to search HOLLIS for primary sources:

• Correspondence
• Description and travel
• Manuscripts
• Notebooks, sketchbooks, etc.
• Personal narratives (refers to accounts of wars and diseases only)
• Pictorial works
• Sources (usually refers to collections of published primary sources)

Include these terms with your topical words in HOLLIS searches. For example: tuberculosis personal narratives

Online Primary Source Collections for the History of Science lists digital collections at Harvard and beyond by topic

Google Book Search, HathiTrust Digital Library and Internet Archives offer books and periodicals digitized from numerous libraries.  Only out-of-copyright, generally post-1923, books are fully viewable.  Each of these three digital libraries allows searching full text over their entire collections.

Google Book Search

HathiTrust Digital Library is a vast digital library of books an dperiodicals. Full text searchs can be limited by standard Subjetc term (as usd in HOOLIS) or by aiuthor or til=tle (useful for periodicals).  Many post-1925 out-of-copyright books, especially government documents, are full text viewable. You can search within copyright books to see what page your search term is on.

Internet Archive also offers a full text search which also can be limited by author, title, subject. For instructions see:  Details on searching HathiTrust and Internet Archive.

The Internet: Archive includes the Medical Heritage Library . Information about the Medical Heritage Library. Searchable full text. Includes:

• US Navy Bureau of Medicine and Surgery Office of Medical History Collection
• State Medical Society Journals    ----  A guide to digitized state medical society journals in the Medical Heritage Library
• Annual reports and other publications of the National Institutes of Health
• UK Medical Heritage Library

Biodiversity Heritage Library

The Online Books Page arranges electronic texts by Library of Congress call numbers and is searchable (but not full text searchable).  Includes books not in Google Books, HathiTrust, or Internet Archive. Has many other useful features.

Contagion: Historical Views of Diseases and Epidemics (1493-1922) provides digitized historical, manuscript, and image resources selected from Harvard University libraries and archives.

Expeditions and Discoveries (1626-1953) features nine expeditions in anthropology and archaeology, astronomy, botany, and oceanography in which Harvard University played a significant role. Includes manuscripts and records, published materials, visual works, and maps from 14 Harvard repositories.

Defining Gender Online: Five Centuries of Advice Literature for Men and Women (1450-1910).

Twentieth Century Advice Literature: North American Guides on Race, Sex, Gender, and the Family.

Finding Primary Sources Online  offers methods for finding digital libraries and digital collections on the open Web   and for finding Digital Libraries/Collections by Region or Language .

Many more general History digital libraries and collections: Library Research Guide for History

More History of Science digital libraries: Library Research Guide for the History of Science .

There may already be a detailed list of sources (a bibliography) for your topic.

For instance:

A bibliography of eugenics , by Samuel J. Holmes ... Berkeley, Calif., University of California press, 1924, 514 p. ( University of California publications in zoology . vol. XXV)  Full text online .

Look for specialized subject bibliographies in HOLLIS Catalog . Example .   WorldCat can do similar searches in the Subject Keyword field for non-Harvard holdings.

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• Articles and Primary Literature
• Get Started

Articles and Primary Literature in Biology

Databases for finding articles.

• Secondary Sources
• Write and Cite in the Sciences
• Sub-discipline Resources
• Chemical and Lab Safety

In the sciences, a primary source describes original research, while a secondary source analyzes or comments on a primary source or sources.   For example, a research article is primary literature because it describes an original experiment and its results, while a review article is secondary literature because it collates multiple research articles to describe the current state of the field.

Examples of primary sources: 

• Research articles
• Theses and dissertations
• Conference proceedings
• Patents 
• Unrefined data sets 

Examples of secondary sources:

• Review articles
• Data compilations

The databases below can help you find primary literature in the sciences. While searching, you can narrow your results to primary literature by using filters on the left of the page.

• Web of Science This link opens in a new window A large interdisciplinary database with a strong collection in the sciences. Filter for primary literature by selecting Article under Document Type on the left of the page. more... less... Easily explore an article bibliography, as well as sources that have cited the article since its publication, via the Citation Network feature. Create a free personal account to keep a comprehensive search history, create search alerts and citation alerts. Additional features related to author and journal profiles are available. Language: English, Russian, French, German, Chinese, Spanish, Japanese, Portuguese, etc. Text Mining: Allowed; only through Clarivate APIs Keywords: Social Science Citation Index Science Citation Index Arts and Humanities Citation Index Conference Proceedings Citation Index Emerging Sources Citation Index WoS Knowledge
• PubMed This link opens in a new window A massive biomedical database run by the NIH, with articles stretching back to the 1950s. Filter primary literature by selecting Clinical Trial under Article Type on the top left of the page. more... less... Includes advanced search tools such as Medical Subject Headings (MeSH) and the Clinical Queries feature. Personalized MyNCBI account features, such as email alerts, are only available by leaving the Library's instance of PubMed and accessing the resource through the open web site (pubmed.gov). Language: English Keywords: Pub Med
• USDA National Agricultural Library This link opens in a new window Why search here? Good for indexed citations from AGRICOLA, PubAg, and the NAL Digital Collections (NALDC) on agriculture topics, food and human nutrition, forestry, aquaculture and fisheries, animal and veterinary sciences. Content type: Abstracts of scholarly articles, book chapters, theses, patents, technical reports. Coverage dates: 1970 - present more... less... Language: English Keywords: Pub Ag U.S. US Department
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• : Aug 19, 2024 5:01 PM
• URL: https://libguides.libraries.claremont.edu/biology

• Online Resources
• Print Reference Books

What Is a Primary Source?

• Finding Primary Sources in the UWRF Library
• Evaluating Internet Sources

A primary source is an original object or document created during the time under study.   Primary sources vary by discipline and can include historical and legal documents, diaries, letters, family records, speeches, interviews, autobiographies, film, government documents, eye witness accounts, results of an experiment, statistical data, pieces of creative writing, and art objects. In the natural and social sciences, the results of an experiment or study are typically found in scholarly articles or papers delivered at conferences, so those articles and papers that present the original results are considered primary sources.  

A secondary source is something written about a primary source. Secondary sources include comments on, interpretations of, or discussions about the original material. You can think of secondary sources as second-hand information. If I tell you something, I am the primary source. If you tell someone else what I told you, you are the secondard source. Secondary source materials can be articles in newspapers or popular magazines, book or movie reviews, or articles found in scholarly journals that evaluate or criticize someone else's original research.

Research versus Review

Scientific and other peer reviewed journals are excellent sources for primary research sources. However, not every article in those journals will be an article with original research. Some will include book reviews and other materials that are more obviously secondary sources . More difficult to differentiate from original research articles are review articles . Both types of articles will end with a list of References (or Works Cited). Review articles are often as lengthy or even longer that original research articles. What the authors of review articles are doing is analysing and evaluating current research or investigations related to a specific topic, field, or problem. They are not primary sources since they review previously published material. They can be helpful for identifying potentially good primary sources, but they aren't primary themselves. Primary research articles can be identified by a commonly used format. If an article contains the following elements, you can count on it being a primary research article. Look for sections entitled Methods (sometimes with variations, such as Materials and Methods), Results (usually followed with charts and statistical tables), and Discussion . You can also read the abstract to get a good sense of the kind of article that is being presented. If it is a review article instead of a research article, the abstract should make that clear. If there is no abstract at all, that in itself may be a sign that it is not a primary resource. Short research articles, such as those found in Science and similar scientific publications that mix news, editorials, and forums with research reports, may not include any of those elements. In those cases look at the words the authors use, phrases such as "we tested," "we used," and "in our study, we measured" will tell you that the article is reporting on original research.

Primary or Secondary: You Decide

The distinction between types of sources can get tricky, because a secondary source may also be a primary source. DoVeanna Fulton's book on slave narratives, for example, can be looked at as both a secondary and a primary source. The distinction may depend on how you are using the source and the nature of your research. If you are researching slave narratives, the book would be a secondary source because Fulton is commenting on the narratives. If your assignment is to write a book review of Speaking Power , the book becomes a primary source, because you are commenting, evaluating, and discussing DoVeanna Fulton's ideas.

You can't always determine if something is primary or secondary just because of the source it is found in. Articles in newspapers and magazines are usually considered secondary sources. However, if a story in a newspaper about the Iraq war is an eyewitness account, that would be a primary source. If the reporter, however, includes additional materials he or she has gathered through interviews or other investigations, the article would be a secondary source. An interview in the Rolling Stone with Chris Robinson of the Black Crowes would be a primary source, but a review of the latest Black Crowes album would be a secondary source. In contrast, scholarly journals include research articles with primary materials, but they also have review articles that are not, or in some disciplines include articles where scholars are looking at primary source materials and coming to new conclusions.

For your thinking and not just to confuse you even further, some experts include tertiary sources as an additional distinction to make. These are sources that compile or, especially, digest other sources. Some reference materials and textbooks are considered tertiary sources when their chief purpose is to list or briefly summarize or, from an even further removed distance, repackage ideas. This is the reason that you may be advised not to include an encyclopedia article in a final bibliography.

The above material was adapted from the excellent explanation written by John Henderson found on Ithaca College's library website http://www.ithacalibrary.com/sp/subjects/primary and is used with permission.

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• Open access
• Published: 18 September 2024

Recommended procedures for managing carious lesions in primary teeth with pulp involvement—a scoping review

• Ilze Maldupa 1 ,
• Waraf Al-Yaseen   ORCID: orcid.org/0000-0002-7071-5074 2 ,
• Julius Giese 1 ,
• Rokaia Ahmed Elagami 3 &
• Daniela Prócida Raggio   ORCID: orcid.org/0000-0002-0048-2068 2 , 3  

BDJ Open volume  10 , Article number:  74 ( 2024 ) Cite this article

55 Accesses

2 Altmetric

Metrics details

• Paediatric dentistry

Managing dental caries in primary teeth with pulp involvement is a significant challenge. Clinical guidelines offer recommendations for effective management.

To identify and analyze policies, guidelines, and recommendations for treating primary teeth with pulp-involved carious lesions, highlighting existing research gaps and setting the foundation for future research.

A comprehensive search was conducted across databases (PubMed, Scopus, Embase, GIN, and LILACS) and grey literature sources (Trip and ProQuest) to identify guidelines, consensus, policy, and position statements on primary teeth pulp therapy and extraction thresholds. Two independent reviewers screened the abstracts and titles, followed by full-text screening.

After removing duplication, of the 1098 records, 14 were selected for analysis. This review examined various treatments for deep caries lesions in primary teeth, including indirect/direct pulp capping, pulpotomy, pulpectomy, lesion sterilization/tissue restoration, and extraction. Time search was restricted to documents published from 30th January 2008 to 30th January 2024, offering insights into evolving clinical practices.

Treatment for carious lesions in primary teeth involving the pulp depends on clinical indications and may involve minimally invasive techniques. Recommended options are indirect pulp capping, pulpotomy, and pulpectomy, while direct capping and tooth removal are discouraged. Further research is needed to address gaps, improve guideline development, and enhance consistency of recommendations.

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Introduction.

Dental caries remains a significant oral health issue affecting approximately half of the global child population, with little change in prevalence over the past few decades (Uribe, Innes, & Maldupa, 2021). Despite efforts to address the problem, complications arising from carries, including pulp damage, continue to impact a considerable number of children (Lin et al., 2019). Pulp damage resulting from caries lesions accounts for nearly 90% of cases and requires effective management strategies [ 1 ].

Primary teeth present unique challenges in the treatment of pulp pathology due to their distinct anatomical and physiological characteristics, as well as the psycho-emotional development of young children [ 2 ]. While the preservation of pulp for as long as possible is advocated as the primary approach, minimally intervention dental (MID) techniques have emerged as successful preventive measures for pulp pathologies [ 3 ]. However, there are clinical scenarios where MID cannot be applied, and immediate treatment becomes necessary for pulp-related complications.

Management of carious lesion with pulp involvement in primary teeth include pulpotomy, pulpectomy, or extraction. The choice of treatment and medications is influenced by various factors. However, pulp therapy treatments often require a child’s cooperation and may involve multiple sessions or general anaesthesia. These factors can heighten anxiety for the child and increase the time and resource burden for their family and dental staff [ 4 ]. Besides, the success rate of endodontic treatment for primary teeth remains a contentious issue [ 5 ]. Consequently, extractions are increasingly favoured as the preferred treatment for pulpal pathology [ 4 ]. Nevertheless, concerns arise regarding space loss, potential orthodontic needs, and the overall impact on the child’s quality of life following premature loss of primary teeth [ 4 ].

To guide healthcare providers in making well-informed decisions regarding the management of caries lesions involving the pulp in primary teeth, various authoritative sources have developed clinical practice guidelines (CPGs), consensus statements, policy documents, and position statements. These resources aim to provide evidence-based recommendations and standardised clinical practices. However, there is considerable variability in the recommendations due to differences in available evidence, contextual factors, and variations in healthcare systems across different countries.

Numerous systematic reviews have synthesized the efficacy of pulp therapy for primary teeth, including Cochrane reviews and other comprehensive analyses [ 6 , 7 ]. These reviews have significantly contributed to our understanding of the outcomes associated with different treatment approaches. Moreover, research has explored the factors influencing clinicians’ decision-making process when choosing between endodontic treatment and extraction for primary teeth with pulp involvement [ 8 ].

Despite these existing systematic reviews and research efforts, the optimal course of action for the preservation or extraction of primary teeth with pulp involvement remains a subject of ongoing debate. CPGs and recommendations have been developed to offer clear and evidence-based guidance. However, the variability in recommendations, based on the best available evidence and contextual factors, underscores the need for further exploration and examination of the existing documents related to the management of caries lesions reaching the pulp in primary teeth.

Hence, this scoping review aims to identify and describe documents (current CPGs, consensus, policies, clinical recommendations and position statements) for managing caries lesions that reached the pulp in primary teeth.

Protocol registration

The research protocol for this scoping review was registered on the Open Science Framework (OSF) platform to ensure transparency and adherence to the planned methodology (OSF registration: ( https://doi.org/10.17605/OSF.IO/APCKG )). The review followed the established methodology for scoping reviews outlined by the Joanna Briggs Institute (JBI) and the report followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Guidelines for Scoping Reviews [ 9 ].

Identification of relevant studies

A comprehensive search strategy was developed in collaboration with experienced researchers and information specialists to identify relevant studies and sources of evidence. Electronic databases, including MEDLINE, Scopus, Embase, GIN, and LILACS, were systematically searched up to 30 th January 2024. Grey literature sources, such as Trip and ProQuest, were also consulted to capture unpublished documents, reports, and guidelines. The search terms and keywords were carefully selected to cover the key concepts of paediatric dentistry, dental caries, clinical practice guidelines, extraction, and pulp therapy (See Appendix  1 ).

Inclusion criteria

This study included recent clinical practice guidelines (CPGs), consensus statements, policy documents, and position statements addressing the threshold for pulp therapy and extraction in primary teeth with pulp involvement. Eligible documents had to be officially endorsed or produced by reputable organisations like government agencies, professional associations, or expert panels, using a systematic consensus approach. In the case of multiple versions, only the latest one was considered. Time search was restricted to the last 20 years (30th January 2004) as older guidelines are likely to be updated or irrelevant. No language restrictions were applied in the search strategy.

Exclusion criteria

Primary and secondary research articles, expert opinions, editorials, and letters to editors, as well as studies involving adult participants or special needs children.

Study selection process

A two-step screening process was conducted by two independent reviewers. In the initial step, titles and abstracts of the identified records were screened to assess their eligibility based on the predefined inclusion and exclusion criteria. Full-text articles were obtained for potentially relevant sources, and two reviewers independently evaluated them for final inclusion in the review. Discrepancies or disagreements between the reviewers were resolved through discussion or consultation with a third reviewer to ensure consensus.

Data extraction

Data extraction was performed using an ad hoc standardised form developed specifically for this scoping review. Two reviewers independently extracted relevant information from the included studies and documents, including publication year, authorship, study design, participant characteristics, methodology, key recommendations, and additional findings deemed relevant. Consistency and accuracy of the extracted data were ensured through cross-checking, and any disagreements were resolved through discussion or involvement of a third reviewer.

Data analysis and presentation

Data analysis aimed to capture the range of recommendations and approaches related to the threshold for pulp therapy and extraction in primary teeth with pulp involvement. A narrative synthesis approach was employed to analyse and present the extracted data. Key themes, concepts, and recommendations from the included studies and documents were systematically organised and summarised. The extracted data were presented using table and graphs to enhance clarity and facilitate understanding. Patterns and variations among the recommendations were identified to provide a comprehensive overview of the existing literature.

Included studies and documents

The initial search process yielded a total of 1098 records from multiple databases and organisations [American Academy of Paediatric Dentistry (AAPD), European Academy of Paediatric Dentistry (EAPD), Scottish Dental Clinical Effectiveness Programme (SDCEP), Qatari, Saudi, Health Ministry of Chile, Brazilian and Iraqi Dental Association] (See Appendix  3 ). After removing duplicates, the titles and abstracts of 417 unique records were screened for eligibility. From this initial screening, 30 papers were selected for a more detailed evaluation. Finally, 14 papers met the inclusion criteria and were included in the in-depth analysis. Figure  1 provides a visual representation of the study selection process following PRISMA-ScR guidelines (See Appendix  2 ) [ 10 ].

The process consists of four stages: Identification, Screening, Eligibility, and Inclusion. Identification: a total of 1098 records were identified from various databases, including PubMed/Medline ( n  = 120), Embase ( n  = 135), Scopus ( n  = 176), Lilacs ( n  = 84), Trip ( n  = 170), ProQuest ( n  = 26), and other sources ( n  = 387). After removing 681 duplicate records, 417 records were screened. Screening: out of the 417 records screened, 387 were excluded based on title and abstract screening, and 30 reports were sought for retrieval. Eligibility: among the 30 reports, 8 were not retrieved. The remaining 22 reports were assessed for eligibility, with 8 reports being excluded due to updated versions being available. Inclusion: ultimately, 14 studies were included in the final review.

Characteristics of included studies and documents

The included studies were primarily sourced from reputable databases, with the highest number of records obtained from the American Academy of Paediatric Dentistry (AAPD) (345), Scopus (176), Trip (170), Embase (135), and PubMed/MEDLINE (120). Additional sources, such as Lilacs (84), ProQuest (26), Scottish Dental Clinical Effectiveness Programme (SDCEP) (16), European Academy of Paediatric Dentistry (EAPD) (14), and GIN (6), also contributed to the final selection of papers. The selected papers focused on the treatment of primary teeth with deep caries lesions and provided insights into extraction, pulpectomy, pulpotomy, and variations within these treatment options.

Treatment modalities

Most CPGs discussed both Direct Pulp Capping (DPC) ( n  = 6) and Indirect Pulp Capping (IPC) ( n  = 8), pulpotomy ( n  = 10) and pulpectomy ( n  = 9) as potential treatment options for specific cases involving deep caries lesions in primary teeth. IPC and DPC techniques were outlined concerning their indications, recommended protocols, and supporting evidence. Additionally, some papers explored the concept of lesion sterilisation/tissue repair (LSTR), albeit being mentioned in only two documents. The use of LSTR for managing carious lesions reaching the pulp in primary teeth was discussed in terms of its effectiveness, limitations, and potential application.

Variations and gaps in recommendations

While the included studies and documents shared commonalities in their recommendations, some variations were observed. These variations were often influenced by contextual factors, such as the healthcare system, resources, and available treatment options in different countries or regions. Additionally, certain aspects of the management of caries lesions in primary teeth with pulp involvement lacked clear consensus or had limited evidence, indicating gaps in the existing literature.

Summary of key findings

The reviewed literature explored various treatment options for primary teeth with deep caries lesions, including extraction, pulpectomy, pulpotomy, and their subdivisions.

Indirect pulp capping

Indirect Pulp Capping was recommended as a successful treatment for vital deciduous teeth affected by deep caries, as it is a MID approach that does not interfere with the natural exfoliation process [ 11 , 12 ]. This treatment is indicated when there is no pulp involvement [ 13 ] and is considered a standard treatment option [ 14 ]. To ensure successful IPC, it is crucial to achieve an excellent seal of the coronal part of the tooth [ 12 ]. The procedure involves selective removal of soft caries tissue, particularly from the dentin-enamel junction, using hand instruments [ 11 , 15 , 16 ]. Subsequently, materials such as zinc oxide eugenol (ZOE), hard-setting calcium hydroxide (Ca(OH)₂), or resin-modified glass ionomer cement (RMGIC) are placed and covered with a preformed crown or adhesive restoration. These procedures have received a grade B recommendation, and level III evidence, and have shown success rates of over 90% after three years [ 16 ]. Alternative approaches, including the use of slow rotary instruments and other biocompatible materials like mineral trioxide aggregate (MTA), were also mentioned (See Fig.  2 ). Compared to pulpotomy treatments, IPC has demonstrated higher long-term success rates [ 11 , 15 ]. Meta-analyses did not find significant differences between bonding agent liners and Ca(OH)₂, with moderate and low evidence after 24–48 months [ 17 ]. In contrast, recommendations from 2005 suggested complete removal of caries and direct pulp capping (DPC) or pulpotomy in cases of iatrogenic pulp exposure due to higher symptom occurrence and uncertain outcomes. Before filling the cavity, Ca(OH)₂ is placed to promote secondary dentin formation (See Fig.  2 ) [ 18 ].

This timeline summarises the evolution of IPC guidelines across various countries and regions from 2005 to 2022. It outlines the indications, recommendations, and levels of evidence in countries such as the UK, Chile, USA, New Zealand, and others. Specific recommendations range from total caries removal to selective caries removal with materials like calcium hydroxide and glass ionomer cement. Evidence levels vary from low to high across different years and regions.

Direct pulp capping (DPC)

The use of DPC as a treatment option is restricted to spot-like pulpal exposure areas due to trauma or mechanical opening during caries removal in cases of non-symptomatic and non-infectious circumstances (See Fig.  3 ), to facilitate dentine structure development [ 16 , 18 , 19 ].

The figure displays DPC guidelines across regions from 2005 to 2022, including the UK, USA, and international recommendations. Indications include traumatic pulp exposures and materials recommended include calcium hydroxide and MTA. Evidence levels range from low to not stated, reflecting the evolving clinical recommendations over the years.

For the purpose of teeth protection from microleakage, Ca(OH)₂ and mineral trioxide aggregate (MTA) have been suggested [ 11 ]. Meta-analyses show no significant difference in success between Ca(OH)₂ and MTA, formocresol (FC) and dentin bonding agents after 24 months. Due to the missing discrepancy of included studies, the quality of evidence was rated as very low [ 17 ]. Prior haemorrhage control by a piece of cotton damped with saline or water has been recommended with grade C and evidence quality level IV [ 16 ].

In general, DPC is not recommended as a regular treatment option for primary teeth [ 15 ]. This might be connected to the elevated cellular density in the pulp tissue of deciduous teeth and poor prognosis [ 20 , 21 ] However, close to the physiological exfoliation time, DPC can be indicated due to less severe consequences (See Fig.  3 ) [ 16 ].

Pulpotomy is a recommended treatment option for primary teeth with profound carious lesions, boasting a 24-month success rate of 82.6% [ 22 ]. However, due to limited direct comparisons, no definitive evidence-supported recommendation can be made regarding the choice between pulpotomy, DPC, and IPC (See Fig.  4 ) [ 14 , 22 ].

This figure highlights pulpotomy guidelines in the UK, Chile, Italy, and other regions from 2005 to 2022. Indications include symptoms of irreversible pulpitis, and materials recommended include formocresol (FC), MTA, and ferric sulfate. Evidence is rated from low to high depending on the year and location. The timeline also covers regional variations in managing pulpotomy procedures.

Pulpotomy is generally indicated for primary teeth with exposed vital pulp or irreversible pulpitis of the coronal pulp, if the underlying tissue is healthy or shows reversible inflammation [ 16 , 17 ]. It can be performed on deciduous teeth at any developmental stage [ 13 ]. Contraindications include severe root resorption, facial cellulitis, abscess history, or specific patient conditions necessitating general anaesthesia [ 23 ]. Pulpotomy for vital pulp in primary molars is a recommended treatment, while non-vital pulpotomy, which differs in procedure and indication, is considered obsolete in most current guidelines.

Some guidelines discourage the use of Ca(OH)₂ during pulpotomy due to compromised results and lower success rates compared to ferric sulphate (FS), mineral trioxide aggregate (MTA), and formocresol [ 12 , 16 , 17 , 19 ].

MTA (87.8%) and formocresol (85%) have shown the highest success rates among recommended treatment choices, leading to a strong recommendation for their use [ 17 ]. Other options are conditionally recommended, and the use of formocresol may raise concerns among parents [ 15 , 16 , 17 ].

MTA, despite higher initial costs, proves to be more cost-effective in the long run due to its greater success rates and reduced need for secondary treatments compared to Ca(OH)₂ [ 17 ]. MTA preserves pulp integrity, reduces inflammation, and promotes tissue formation, while Portland cement is considered a low-cost alternative [ 24 ].

Additional research is needed to determine specific recommendations for lining materials, caution is advised regarding the combination of FS and eugenol, and control of haemorrhage is essential during treatment [ 16 , 18 , 24 ].

Stainless steel crowns are recommended as a permanent restoration after pulpotomy, while composite resin and amalgam can be used for deciduous teeth with minor structural damage [ 11 ].

Pulpectomy is a recommended treatment for restorable primary teeth with necrosis, irreversible pulpitis, root resorption, and other pathologies [ 11 ]. It is preferred over LSTR in the absence of root resorption. Pulpectomy is generally not recommended as a first-line treatment for deep caries in vital primary molars due to the effectiveness of more conservative alternatives like indirect pulp capping or pulpotomy. However, it may be used instead of extraction when tooth loss could harm dental health and long-term occlusion, or if there is no permanent successor [ 12 ].

Prior to treatment, a periapical radiograph is taken for diagnosis, and anaesthesia is administered [ 4 ]. Root canal shaping can be done with rotary or hand files, followed by irrigation using sodium hypochlorite or alternative solutions [ 11 , 15 ]. Canals are dried before using zinc oxide eugenol (ZOE) cement or calcium hydroxide (Ca(OH)₂) with iodoform paste for obturation [ 11 , 15 ].

Different approaches exist for pulpectomy depending on the condition, such as two-stage or one-stage procedures [ 18 ]. The Italian Ministry of Health recommends pulpectomy for non-vital primary teeth in specific developmental stages and with clinical signs like abscesses, fistula, and pain [ 2 ]. The use of Ca(OH)₂ combined with iodoform paste is advantageous, although ZOE is also suggested [ 2 ]. Irrigation should be performed using hypochlorite, saline, or chlorhexidine [ 16 ].

The Federal University of Rio de Janeiro (UFRJ) recommends specific irrigation techniques and materials for obturation, such as ZOE, glass ionomer cement (GIC), or heated gutta-percha. The heated gutta-percha is used specifically to seal the canal orifice, not to fill the canals [ 25 ]. Preformed crowns are suggested for excellent coronal seal [ 16 ]. Pulpectomy success rates range from 59% to 69% for teeth with root resorption and 84% to 90% for those without [ 25 ]. Extraction may be necessary if fistula or abscess persists after Ca(OH)₂ [ 25 ]. The Dubai Health Authority limits pulpectomy to primary teeth with less than one-third root resorption and without facial cellulitis or abscess [ 23 ]. Considerations for pulpectomy include long-term retention of second deciduous molars and stable occlusion, with conservative treatments preferred for profound carious lesions (See Fig.  5 ).

The pulpectomy timeline from 2005 to 2022 illustrates recommendations from the UK, Chile, USA, and other countries. It covers the management of irreversible pulpitis and related pathology, with recommendations including the use of zinc oxideeugenol, MTA, and root canal instrumentation. Evidence levels range from low to moderate across different regions.

Lesion sterilisation/tissue repair (LSTR)

LSTR is a possible treatment option for primary teeth experiencing clinical symptoms of irreversible pulpitis, fistula formation, and other pathologies (see Fig.  6 ) [ 11 , 15 ]. It is considered preferable over pulpectomy in cases of root resorption and teeth expected to exfoliate within one year. The treatment involves establishing access to the pulp chamber and augmenting the orifices. Phosphoric acid is used to cleanse the chamber, followed by rinsing and drying. Subsequently, a paste containing ciprofloxacin, metronidazole, and clindamycin, along with macrogol and polyethylene, is placed in the affected areas. It is important to avoid the incorporation of tetracycline into the antibiotic mix. Finally, glass ionomer cement (GIC) and a stainless-steel crown are placed [ 11 , 15 ].

This figure outlines LSTR treatment guidelines between 2005 and 2022 in regions like the USA and international contexts. The timeline reflects recommendations for disinfecting root canals using antibiotics like ciprofloxacin and metronidazole for cases of irreversible pulpitis and root resorption. Evidence is generally not stated.

Extractions

Extraction is indicated for primary teeth in the following situations: teeth approaching exfoliation, teeth that are non-restorable due to extensive caries or uncontrolled pulp haemorrhage [ 16 , 18 , 20 , 26 ]. In addition, pulpectomy with repeated medication application without symptom relief or continuous exudation is also a reason for extraction [ 25 ]. (See Fig.  7 ).

From 2005 to 2022, this figure tracks extraction guidelines in the UK, Chile, USA, and other regions. Indications include nonrestorable teeth with extensive decay or advanced root resorption. Recommendations include balanced extractions and use of chlorhexidine (CHX) irrigation. Evidence levels vary from low to not stated.

Balanced bilateral extractions may be considered for primary canines, and in cases where there is absence of the contralateral tooth, extraction may be indicated for the first deciduous molars, provided that the jaw space is not excessively crowded [ 16 , 18 ]. However, primary incisors are less frequently subjected to extraction [ 18 ]. It is important to consider the need for space maintainers when the development of permanent root formation does not exceed one-third of its completion [ 25 ].

In addition to clinical factors, such as tooth condition and stage of eruption, other factors including patient cooperation, social factors, and medical conditions should be considered when deciding on extraction [ 20 ]. Furthermore, the attitude of the patient and parents, as well as the number and complexity of required treatments, should be also considered [ 16 , 18 ]. It is generally recommended to avoid extractions during initial dental visits [ 13 , 20 ]. Whenever possible, extraction should be avoided in cases of crowding, absence of underlying permanent teeth, and situations that may cause increased stress for the patient [ 18 ].

The management of caries lesions that reach the pulp in primary teeth presents a complex challenge for dental professionals. CPGs play a crucial role in providing evidence-based recommendations for the treatment of such cases. This scoping review aimed to identify and describe documents, including CPGs, consensus statements, policies, and clinical recommendations, pertaining to the management of caries lesions that reached the pulp in primary teeth. Hence, this review provides valuable insights into the variations in thresholds and recommendations for different treatment procedures. Although our focus was on published documents, it is important to note that we could not verify whether these documents utilised the best available evidence to formulate their recommendations or if they had low risk of bias.

The analysis of the included documents revealed variations in thresholds and recommendations for different treatment procedures. These variations stem from differences in the interpretation of the available evidence, clinical judgement, and priorities of different dental organizations and professional societies.

The comparison of indications for each procedure among different CPGs provides valuable insights into the diverse perspectives and considerations when managing caries lesions that reach the pulp in primary teeth. These variations in recommendations reflect the complexities of clinical decision-making and the diverse approaches taken by different guidelines.

For instance, the AAPD guidelines recommend Indirect Pulp Capping as a standard treatment option for vital primary teeth with deep caries lesions but without pulp involvement [ 16 ]. IPC is widely practiced in the United States and has shown favourable outcomes. In contrast, the EAPD guidelines also support IPC but provide more specific indications, such as minimal pulp involvement and limited symptoms [ 12 ].

When considering direct pulp capping and pulpotomy, guidelines offer varying recommendations. The AAPD guidelines suggest DPC for spot-like pulpal exposures resulting from trauma or mechanical opening during caries removal [ 19 ]. On the other hand, the SDCEP guidelines discourage the routine use of DPC and instead recommend pulpotomy as a treatment option [ 13 ].

The indications for pulpotomy also show variations among guidelines. The IAPD guidelines recommend pulpotomy for primary teeth with exposed vital pulp or irreversible pulpitis of the coronal pulp [ 15 ]. However, specific indications provided by different guidelines may vary, taking into account factors such as clinical signs, developmental stages, and the prevalence of dental conditions.

Similarly, the indications for pulpectomy vary among guidelines. The AAPD guidelines recommend pulpectomy for restorable primary teeth with necrosis, irreversible pulpitis, root resorption, or other pathologies [ 11 ]. In contrast, guidelines from other sources may provide more specific indications based on their own research and clinical experience.

These variations in recommendations highlights the influence of context on treatment recommendations. Guidelines developed in different regions may reflect the specific needs and resources available in those areas. Furthermore, the availability of materials and resources can significantly impact the treatment options recommended in the guidelines. Different regions may have varying access to materials such as Ca(OH)₂, MTA, or formocresol. These variations in material availability can lead to differences in the recommended treatment modalities. Cost-effectiveness of materials play a key role in the treatment choices outlined in the guidelines. The review evidence highlights the departure from historical practices, with the more recent CPGs no longer endorsing complete caries removal [ 21 ]. Similarly, the reconsideration of calcium hydroxide (Ca(OH)₂) usage, previously employed for secondary dentin formation before cavity filling, reflects this evolving perspective. This shift aligns with our growing understanding of cariology, emphasising minimally invasive procedures to preserve teeth tissue whenever possible [ 27 ]. Despite these advancements, the adoption of these guideline points among clinicians remains limited [ 28 ]. Addressing this gap may necessitate broader dissemination of updated guidelines, targeted educational initiatives, and ongoing efforts to bridge the translation gap between evidence-based recommendations and clinical implementation.

Another important consideration is the publication and development process of the guidelines. While guidelines aim to provide evidence-based recommendations, the level of detail and transparency in their development can vary. Some guidelines may provide extensive information on the underlying evidence, the grading of recommendations, and the consensus process followed. An example of such comprehensive guidelines is the Guidelines for the Management of Dental Emergencies by the SDCEP, which provide clear explanations of the evidence base, and the consensus process used [ 13 ]. On the other hand, some guidelines may lack sufficient information on the level of evidence, or the specific studies considered during their development.The lack of transparency and detail in guideline development makes it challenging to understand the rationale behind certain recommendations and hampers the ability to compare and reconcile differences between guidelines. To enhance the transparency and quality of guidelines, future efforts should prioritize the adherence to established guideline development methodologies, such as those recommended by Guidelines International Network. This includes clearly outlining the process for evidence synthesis, the grading of recommendations, and the involvement of multidisciplinary experts. The reporting quality of clinical practice guidelines exhibits significant variability. A previous study assessing the reporting quality of CPGs in paediatric dentistry has indicated suboptimal adherence to quality standards, underscoring the need for future improvement in their applicability. Implementation of standardised checklists such as the Appraisal of Guidelines for Research and Evaluation (AGREE) is imperative during CPG development processes to ensure methodological rigour and transparency in newly developed guidelines, before their adoption into clinical practice.

Among the myriad recommended treatments for various pulp conditions, a fundamental principle must remain unequivocal—treating patients based on the minimum intervention approach. In navigating the therapeutic choices, the essence of the Hippocratic principle, “primum non nocere” (first, do no harm). Thus, as practitioners, we are reminded to balance the intricacies of diverse treatment modalities with a commitment to the overarching goal of delivering care that is both effective and minimally invasive.

There are significant variations in guidelines for diagnosing and managing caries lesions that reach the pulp in primary teeth, reflecting differences in evidence interpretation, clinical judgement, and organisational priorities.

For caries with pulp involvement, guidelines differ: the AAPD advocates treating small pulpal exposures due to trauma or mechanical opening with direct pulp capping, while the SDCEP recommends more conservative approaches. The IAPD focuses on specific clinical signs and developmental stages to guide treatment, such as the extent of pulp involvement and the child’s age.

Regional needs and resources influence treatment recommendations, including the availability of materials like calcium hydroxide, mineral trioxide aggregate (MTA), or formocresol, and cost-effectiveness considerations. Recent guidelines favour minimally invasive procedures and reconsider the use of traditional materials like calcium hydroxide.

Transparency and methodological rigour in guideline development vary. Comprehensive guidelines, such as those from the SDCEP, provide clear evidence bases and consensus processes. Future guidelines should adhere to established methodologies to ensure transparency and methodological rigour.

Why this paper is important to paediatric dentists:

There is significant variation in guidelines for managing caries in primary teeth, influenced by regional contexts, material availability, and opaque guideline development processes. Understanding this variation is crucial for paediatric dentists to interpret and apply guidelines appropriately.

Adhering to clear guideline development methodologies and transparency about the rationale and evidence behind recommendations is needed to promote consistency and confidence in guidelines. This allows paediatric dentists to make properly evidence-based decisions.

Enhancing the quality and usability of guidelines on managing dental caries will facilitate decision-making for paediatric dentists seeking to provide optimal patient care. Reducing ambiguity supports the provision of appropriate care tailored to specific contexts.

Data availability

The data that support the findings of this study are available in the Appendix  3 .

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Acknowledgements

The study was funded by Fundamental & Applied Research Projects (FLPP), Latvian Council of Science wide no. lzp-2022/1-0047, IEVA—Implementation of the Evidence-Based Paediatric CAries Management Strategies in Latvian Clinical Practice—an Evidence Transfer Study. The Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES; Coordination for the Improvement of Higher Education Personnel)—finance code 001 granting scholarships to RAE. The funders had no role in the conduct of the study, the analysis of the data or the decision to submit the manuscript for publication.

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IM, DPR, and WA conception and design of the study; IM, JG, RAE, and WA data acquisition; JG, IM and DPR. data analysis and interpretation; WA, IM, RAE AND DPR drafted the manuscript; IM, WA, RAE, DPR revised and gave final approval of the manuscript.

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Maldupa, I., Al-Yaseen, W., Giese, J. et al. Recommended procedures for managing carious lesions in primary teeth with pulp involvement—a scoping review. BDJ Open 10 , 74 (2024). https://doi.org/10.1038/s41405-024-00259-8

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Received : 19 June 2024

Revised : 04 August 2024

Accepted : 07 August 2024

Published : 18 September 2024

DOI : https://doi.org/10.1038/s41405-024-00259-8

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