# How to Cite Sources in a Literature Review ## Quick Answer - Choose your citation style before writing based on your target journal or assignment requirements, then apply it consistently to every source. - Use a reference manager to capture bibliographic details at first reading so you never lose source information. - Paraphrase carefully and cite the original idea even when you change the wording, because plagiarism applies to ideas, beyond exact phrases. ## Why Citation Style Matters in a Literature Review A literature review is a structured examination of existing research on a topic. It shows readers what is known, what is contested, and where gaps remain. Citation style is the system that connects each claim in your review to its original source. Without consistent citations, readers cannot verify your statements, trace the development of ideas, or distinguish your analysis from the work of others. Different academic fields and journals require different citation formats. Life science journals commonly use author-date systems like APA or numbered systems like Vancouver. Humanities and social science assignments often require MLA. The style you use signals your field and your attention to disciplinary norms. When you submit to a specific journal, that journal's instructions to authors will specify the required style. Following those instructions is part of meeting the journal's expectations for manuscript preparation. The [National Library of Medicine](https://www.ncbi.nlm.nih.gov/books) hosts authoritative biomedical books and research method references that can help you understand how citation practices operate within the health sciences. These resources describe the conventions that journals in medicine and biology expect from authors. ## At a Glance: Citation Styles Compared | Style | Common Use | In-Text Format | Reference List Format | Key Rule | |-------|-----------|----------------|----------------------|----------| | APA 7th | Psychology, education, life sciences | (Author, Year) | Author, A. A. (Year). Title. Source. | Include year in every citation | | MLA 9th | Humanities, language studies | (Author Page) | Author Last Name, First Name. Title. Publisher, Year. | Page number required for direct quotes | | Vancouver | Biomedical journals | Numbered | 1. Author AA. Title. Journal. Year,Vol(Issue):Pages. | Cite by number in order of appearance | The table above shows the three styles most often required in academic writing. APA emphasizes the date because research fields value currency. MLA emphasizes page numbers because humanities scholars work closely with specific passages. Vancouver uses numbers because biomedical readers need compact citations that do not interrupt dense scientific prose. Your choice depends on the venue. Check the journal's author guidelines or your assignment prompt first. If no style is specified, APA is a reasonable default for life science and social science work. Vancouver is common for clinical and biomedical submissions. MLA suits humanities coursework. ## Core Principles of Ethical Citation ### Citation Is a Contract With Your Reader When you cite a source, you tell your reader where an idea came from. This allows them to check your interpretation against the original. It also gives credit to the researcher who did the work. The [Committee on Publication Ethics](https://publicationethics.org/core-practices) describes the responsibilities that researchers hold toward the scholarly record. These responsibilities include handling data properly, managing conflicts of interest, and ensuring that published work is honest and transparent. Citation is part of that honesty. When you present another researcher's finding without attribution, you misrepresent the state of knowledge. You also make it impossible for readers to distinguish established findings from your own contributions. A literature review that does not cite properly fails its primary purpose, which is to map the intellectual territory of a field. ### Plagiarism Is About Ideas, beyond Words Many writers believe plagiarism only occurs when you copy exact sentences. This is incorrect. Plagiarism occurs when you present someone else's ideas, data, or reasoning as your own, even if you have rewritten the wording completely. Paraphrasing without citation is still plagiarism. The [Committee on Publication Ethics](https://publicationethics.org/core-practices) addresses misconduct in research and publication. Plagiarism is a form of misconduct because it misrepresents the origin of intellectual work. In a literature review, every claim that comes from a specific study needs a citation, whether you quote it directly, paraphrase it, or summarize it. ### Citation Supports Verification A literature review is also a summary. It is an argument built from evidence. Each citation is a pointer to evidence your reader can examine. When you cite a study, you invite scrutiny of that study's methods, findings, and limitations. This is how scholarly knowledge advances. The [EQUATOR Network](https://www.equator-network.org/) promotes transparent reporting in health research, which includes making methods and results clear enough for others to evaluate. Proper citation is the mechanism that connects your review to the transparent reporting standards of your field. ## Choosing the Right Citation Style ### Journal Requirements Come First Before you write a single sentence, determine the citation style required by your target journal or your instructor. Most journals publish detailed instructions for authors on their websites. These instructions specify the reference format, in-text citation style, and often provide templates for common source types. Following these instructions is not optional. Manuscripts that do not conform to journal style are often returned for revision before peer review begins. The [National Library of Medicine](https://www.ncbi.nlm.nih.gov/books) provides access to authoritative references on research methodology and publication practices. These resources can help you understand the conventions used in biomedical publishing, including how citations function within the broader structure of a scientific paper. ### APA Style for Life Sciences and Social Sciences APA style uses an author-date system. In the text, you place the author's last name and the year of publication in parentheses. The reference list at the end provides full bibliographic details arranged alphabetically by author. APA is common in psychology, education, nursing, and many life science fields. It emphasizes the currency of research, which is why the year appears in every in-text citation. When you cite multiple works by the same author, the year distinguishes them. When you cite a work with two authors, both names appear in every citation. Works with three or more authors use the first author's name followed by "et al." ### MLA Style for Humanities MLA style uses an author-page system. In the text, you place the author's last name and the page number where the quoted or paraphrased material appears. The works cited list at the end provides full details arranged alphabetically. MLA is common in literature, languages, and cultural studies. The page number requirement reflects the humanities tradition of close reading, where scholars need to locate specific passages within longer works. If you are writing a literature review for a humanities course, MLA is likely the expected style. ### Vancouver Style for Biomedical Journals Vancouver style uses numbered citations. Each source receives a number based on the order it first appears in the text. In-text citations appear as superscript numbers or numbers in brackets. The reference list at the end is numbered to match. Vancouver is common in medical and biomedical journals. It keeps the text clean and uncluttered, which matters in clinical writing where dense information is the norm. The numbered system also makes it easy to cite the same source multiple times without repeating full author names and years. ## Building Your Reference Management Workflow ### Capture Source Details at First Reading The most common citation failure is losing source information. You read an article, take notes, and later cannot remember the journal name, volume number, or page range. This problem is preventable with a consistent workflow. When you first encounter a source, record its complete bibliographic details immediately. This includes authors, year, title, journal or book title, volume, issue, pages, and DOI or URL. A reference manager can automate this process. Tools like Zotero, Mendeley, or EndNote capture citation details from databases and websites with a single click. The [National Institutes of Health](https://grants.nih.gov/) provides guidance on grant applications and research conduct. While this guidance focuses on funding, it reflects the broader expectation that researchers maintain accurate records throughout the research process. Your citation records are part of your research data. ### Use a Reference Manager From the Start A reference manager stores your sources in a searchable database. It can generate in-text citations and reference lists in multiple styles. This saves time and reduces errors. When you switch from APA to Vancouver, the reference manager reformats everything automatically. The [ORCID for Researchers](https://info.orcid.org/researchers) page explains how researchers can maintain a persistent digital identifier that distinguishes them from others with similar names. While ORCID is primarily about author identity, it reflects the same principle as reference management: accurate record keeping is essential to scholarly work. Your reference manager is the tool that keeps your citation records accurate. ### Organize Sources by Theme, Not by Reading Order A literature review is organized by theme or argument, not by the order you read sources. Your reference manager should reflect this structure. Create folders or tags for each theme in your review. When you find a source relevant to multiple themes, tag it with multiple labels. This organization makes writing easier. When you draft a section on a specific theme, you can pull up all relevant sources in your reference manager and see what you have. You can also identify gaps in your coverage, which helps you plan additional searches. ## How to Paraphrase Without Plagiarizing ### Understand the Source Before You Rewrite Paraphrasing requires comprehension. You cannot accurately restate an idea you do not understand. Read the source passage carefully. Identify the main claim, the supporting evidence, and the reasoning that connects them. Then set the source aside and write the idea in your own words. This process ensures your paraphrase reflects your understanding instead of a superficial rewording. A good paraphrase captures the meaning of the original in different language and structure. It is not a word-for-word substitution where you replace a few synonyms. ### Change Structure and Vocabulary Effective paraphrasing changes both the sentence structure and the vocabulary. If the original is a long complex sentence, break it into shorter sentences. If the original uses passive voice, consider active voice. Replace technical terms with synonyms only when the synonym is accurate. The [EQUATOR Network](https://www.equator-network.org/) promotes clear and transparent reporting in health research. Clear writing is the goal of paraphrasing as well. Your paraphrase should be easier to understand than the original, not harder. If your paraphrase is more confusing than the source, you have not done your job. ### Always Cite the Paraphrase A paraphrase requires a citation just as a direct quote does. The citation tells the reader that the idea originated with the cited source, even though the wording is yours. This is the distinction between plagiarism and legitimate scholarly practice. The [Committee on Publication Ethics](https://publicationethics.org/core-practices) treats plagiarism as a serious breach of publication ethics. Citing your paraphrases is the practice that keeps you on the right side of that line. When in doubt, cite. An unnecessary citation is a minor issue. A missing citation is a potential misconduct allegation. ### Use Direct Quotes Sparingly Direct quotes are appropriate when the original wording is important, such as when you are analyzing a specific definition or when the author's phrasing is particularly memorable. In most literature reviews, paraphrases and summaries should dominate. Direct quotes should be reserved for passages where the exact wording matters. When you do quote directly, copy the wording exactly. Place quotation marks around the quoted material. Include the page number in your citation so readers can locate the passage. For sources without page numbers, use paragraph numbers or section headings if available. ## Managing Sources for a Systematic Literature Search ### Define Your Search Strategy Before You Search A literature review requires a systematic approach to finding sources. Before you search, define your research question and identify the key concepts. Determine which databases are most relevant to your field. For life science topics, PubMed and Web of Science are common starting points. For social science topics, PsycINFO and Scopus may be more appropriate. The [National Library of Medicine](https://www.ncbi.nlm.nih.gov/books) provides access to research methods resources that describe systematic approaches to literature searching. These resources explain how to construct search strings, use Boolean operators, and document your search process. ### Document Your Search Process A systematic literature search is documented so that others can reproduce it. Record the databases you searched, the date of each search, the search terms you used, and the number of results you obtained. This documentation is part of the methods section of your literature review. The [EQUATOR Network](https://www.equator-network.org/) provides reporting guidelines for health research, including guidelines for systematic reviews. These guidelines specify what information about the search process should be reported. Even if you are not writing a full systematic review, following these reporting principles strengthens your literature review. ### Screen Sources for Relevance and Quality Not every search result belongs in your review. Screen sources for relevance to your research question and for quality of the research. Consider the study design, sample size, and whether the findings have been replicated. Consider the source's publication venue and whether it is peer reviewed. The [Committee on Publication Ethics](https://publicationethics.org/core-practices) describes the responsibilities of authors and reviewers in maintaining the quality of the scholarly record. Your screening process is your contribution to that quality. By including only relevant, credible sources, you ensure your literature review is built on solid evidence. ## Using a Literature Review Matrix ### What a Matrix Does A literature review matrix is a table that organizes your sources by key characteristics. Common columns include author and year, research question, methods, sample, key findings, and limitations. The matrix helps you compare sources across these dimensions and identify patterns in the literature. The matrix is a working document, not a final product. You update it as you read new sources and refine your understanding of the field. It serves as the bridge between your reading and your writing. ### How to Build a Matrix Create a table with columns for the information you need to compare. Start with the basics: author, year, and full citation. Add columns for the research question, methods, findings, and limitations. Add a column for how the source relates to your review's themes. As you read each source, fill in the relevant row. Be concise. The matrix is for your reference, not for publication. Use abbreviations and short phrases that you understand. ### How the Matrix Improves Your Citations The matrix prevents citation errors by keeping all source information in one place. When you write a section of your review, you can see at a glance which sources support which claims. You can also see which sources contradict each other, which helps you write a more nuanced analysis. The [National Institutes of Health](https://sharing.nih.gov/data-management-and-sharing-policy) describes expectations for data management and sharing in NIH-funded research. While this policy focuses on research data, the principle applies to your citation records as well. Your matrix is a form of research documentation that supports the integrity of your work. ## Common Citation Mistakes and How to Avoid Them ### Citing a Source You Have Not Read This is the most serious citation error. When you cite a source you have not read, you risk misrepresenting its content. You also risk propagating errors if you are relying on another author's description of the source. The [Committee on Publication Ethics](https://publicationethics.org/core-practices) emphasizes accuracy and honesty in the scholarly record. Citing sources you have not read violates both principles. If you must cite a source you cannot access, use secondary citation format and make clear that you are citing it through another work. ### Incorrect Bibliographic Details A citation with the wrong year, volume, or page number is nearly useless. Readers cannot locate the source. This error often occurs when you transcribe details from memory or from an incomplete record. The solution is to capture bibliographic details at first reading and verify them before submission. Your reference manager can help, but you should still spot-check citations against the original sources or database records. The [Citation Checker](/tools/citation-checker) does this spot-check for a whole list, comparing each entry's year, volume and pages with its Crossref or PubMed record. ### Inconsistent Style Application Mixing APA in-text citations with Vancouver reference list formatting confuses readers and signals carelessness. Consistency is the most basic requirement of citation practice. The solution is to choose your style at the start and apply it throughout. If you use a reference manager, set the style before you begin writing. If you are writing manually, keep a style guide handy and check every citation against it. ### Missing Citations for Paraphrased Ideas As discussed above, paraphrases require citations. Missing citations for paraphrased material is a form of plagiarism, even when the wording is original. The solution is to develop the habit of citing as you write. When you draft a sentence that draws on a source, add the citation immediately. Do not plan to add citations later. Later is when citations get lost. ## Records and Measurements for Citation Accuracy ### What to Track Maintain a record of every source you consult, beyond the sources you cite. This record should include the full bibliographic details, the date you accessed the source, and notes on how the source relates to your review. The [National Institutes of Health](https://sharing.nih.gov/data-management-and-sharing-policy) describes expectations for documenting research data. Your citation records are part of your research documentation. They should be complete enough that another researcher could reconstruct your search and verification process. ### How to Verify Your Citations Before you submit your literature review, verify every citation. Check each reference list entry against the original source or a database record. Verify that every in-text citation appears in the reference list and that every reference list entry is cited in the text. This verification process is time-consuming but essential. Citation errors undermine your credibility and can delay publication. The [EQUATOR Network](https://www.equator-network.org/) provides resources for transparent reporting that include guidance on accurate citation practice. ## Common Failure Patterns in Literature Review Citations ### The Lost Source Problem You read an article, take notes, and later cannot find the full citation. This happens when you do not capture bibliographic details at first reading. The solution is to record full details immediately, either in a reference manager or a dedicated notes file. ### The Citation Chain Problem You read a review article that cites a primary study. You want to cite the primary study but have not read it. If you cite the primary study based only on the review article's description, you risk misrepresenting it. The solution is to read the primary study before citing it. If you cannot access it, cite the review article instead and note that it discusses the primary study. ### The Style Drift Problem You start writing in APA, switch to Vancouver midway, and do not notice until submission. This happens when you do not set your citation style at the start. The solution is to choose your style before writing and use a reference manager to enforce consistency. ### The Overcitation Problem You cite every sentence, even sentences that state common knowledge or your own analysis. This clutters your text and obscures which claims actually need support. The solution is to cite claims that come from specific sources and leave common knowledge uncited. When in doubt, ask whether a reader would need to verify the claim. ## Welfare and Safety Context for Research Integrity ### Protecting Your Academic Standing Citation errors can have serious consequences. Plagiarism, whether intentional or accidental, can result in course failure, degree revocation, or retraction of published work. The [Committee on Publication Ethics](https://publicationethics.org/core-practices) describes the consequences of misconduct for the scholarly record and for individual researchers. The safety context here is professional. Your citation practice protects your reputation and your career. A single plagiarism allegation can damage years of work. The cost of careful citation is small compared to the cost of a misconduct finding. ### Protecting the Scholarly Record Your citations are part of a larger system of scholarly communication. When you cite accurately, you contribute to a record that other researchers can trust. When you cite carelessly, you introduce errors that propagate through the literature. The [EQUATOR Network](https://www.equator-network.org/) promotes transparent reporting because the scholarly record is only as reliable as the practices that produce it. Your citation practice is part of that reliability. ## Professional Escalation Criteria ### When to Seek Help If you are unsure which citation style to use, ask your instructor or check the journal's author guidelines. If you are unsure whether a paraphrase requires a citation, cite it. If you are unsure whether a source is credible, ask a librarian or your research advisor. The [National Library of Medicine](https://www.ncbi.nlm.nih.gov/books) provides access to research methods resources that can answer many citation questions. Librarians are also excellent resources for citation questions. They can help you choose a style, use a reference manager, and verify citations. ### When to Consult an Editor or Advisor If you are preparing a manuscript for journal submission, consider consulting a professional editor or your research advisor before submission. They can catch citation errors you have missed and help you conform to journal style. The [National Institutes of Health](https://grants.nih.gov/) provides guidance on preparing grant applications, which includes expectations for accurate citation of prior work. If you are applying for funding, your citations are part of your application's credibility. ### When to Report a Problem If you discover that you have inadvertently plagiarized material, correct it immediately. If the material has already been published, contact the journal editor to discuss correction or retraction. The [Committee on Publication Ethics](https://publicationethics.org/core-practices) provides guidance on handling publication errors and misconduct. ## Frequently Asked Questions ### What is the difference between a reference list and a bibliography? A reference list includes only the sources you cited in your text. A bibliography includes all sources you consulted, whether or not you cited them. Most journals require a reference list. Some assignments require a bibliography. Check your instructions to know which is expected. ### How do I cite a source I found cited in another article? This is called a secondary citation. Cite the source you actually read, not the source you could not access. In APA format, you would cite the secondary source and note that it discusses the primary source. In Vancouver format, you would cite the secondary source by number. Avoid secondary citations when possible by reading the primary source directly. ### How many sources should a literature review cite? There is no universal number. The appropriate number depends on your topic, the scope of your review, and the requirements of your assignment or journal. A focused review on a narrow topic may cite fewer sources than a broad review of a large field. Quality matters more than quantity. Your citations should cover the key studies in your area and support your argument. ### Can I cite a website in a literature review? Yes, but use websites selectively. Websites can be useful for citing reports, datasets, and official documents. However, websites are often less stable than journal articles and may change or disappear. If you cite a website, include the access date and verify that the URL is correct. Prefer peer-reviewed journal articles for scientific claims. ### How do I cite a source with multiple authors? The format depends on your citation style. In APA, works with two authors cite both names in every citation. Works with three or more authors cite the first author followed by "et al." In Vancouver, the number system means you do not list authors in the text at all. Check your style guide for the specific rules. ### What is a DOI and do I need to include it? A DOI, or digital object identifier, is a permanent link to a digital object such as a journal article. Many citation styles require DOIs in reference list entries because they provide stable access to the source. If a source has a DOI, include it. If it does not, include the URL instead. ### How do I avoid plagiarism when taking notes? Take notes in your own words instead of copying passages verbatim. When you do copy a passage, put it in quotation marks and note the page number immediately. Record the full citation for every source in your notes. This practice ensures you have the information you need to cite correctly when you write. ### What should I do if I find a citation error in my submitted work? Contact the journal editor or your instructor immediately. Explain the error and provide the correct information. If the error is minor, such as a wrong page number, a correction may be sufficient. If the error involves plagiarism, the consequences may be more serious. The [Committee on Publication Ethics](https://publicationethics.org/core-practices) provides guidance on handling such situations. ## Using the Evidence | Source | Best use in this topic | Important limitation | |---|---|---| | [Research Methods Resources](https://www.ncbi.nlm.nih.gov/books) | official guidance | Check the linked page for current local requirements | | [EQUATOR Network](https://www.equator-network.org/) | official guidance | Check the linked page for current local requirements | | [Core Practices](https://publicationethics.org/core-practices) | official guidance | Check the linked page for current local requirements | ## Related Articles - [How to Cite Scientific Papers: A Guide to Citation Formats](/blog/guides/how-to-cite-scientific-papers-a-guide-to-citation-formats) - [Peer Review Metrics: What They Are and How to Use Them](/blog/guides/peer-review-metrics-what-they-are-and-how-to-use-them) - [Scientific Literature Review: A Reproducible Search and Synthesis Workflow](/blog/careers/scientific-literature-review-a-reproducible-search-and-synthesis-workflow) - [Scientific Literature Review Format: A Reproducible Structure for Researchers](/blog/careers/scientific-literature-review-format-a-reproducible-structure-for-researchers) - [Choosing the Right Citation Style for Your Scientific Paper](/blog/guides/choosing-the-right-citation-style-for-your-scientific-paper) ## References and Further Reading - [Research Methods Resources](https://www.ncbi.nlm.nih.gov/books). National Library of Medicine. > This article is educational and does not replace institutional policy, professional advice, or applicable safety and regulatory requirements.