Citing sources in a paper involves two components: a brief marker in the text where you use someone else’s information, and a full reference entry at the end of your paper that gives readers everything they need to find that source. The exact format depends on which citation style your instructor or field requires, but the underlying logic is the same across all of them.
Pick the Right Citation Style
Before you format a single citation, confirm which style your assignment requires. Your syllabus, assignment sheet, or instructor will usually specify one. If nothing is stated, the convention in your field is the default:
- APA (American Psychological Association) is standard in education, psychology, and the sciences. The current edition is the 7th.
- MLA (Modern Language Association) is used in the humanities, including English, literature, and philosophy. The current edition is the 9th.
- Chicago/Turabian is common in business, history, and the fine arts. The 18th edition was published in 2024.
Each style has its own rules for punctuation, capitalization, ordering of elements, and page formatting. Mixing styles in one paper is a quick way to lose points, so commit to one and stick with it throughout.
How In-Text Citations Work
An in-text citation is a short reference placed right where you quote, paraphrase, or summarize someone else’s work. Its job is to point the reader to the full entry in your reference list so they can verify or explore the source. There are two main systems for doing this.
Parenthetical Citations
APA and MLA both use parenthetical citations, meaning you place a brief note inside parentheses within your sentence. In APA, you include the author’s last name and the year of publication, like (Smith, 2022). If you’re quoting directly, add the page number: (Smith, 2022, p. 14). In MLA, you include the author’s last name and the page number, without a year: (Smith 14). If you’ve already named the author in the sentence itself, you can drop the name from the parentheses and include only the year or page number.
Footnotes and Endnotes
Chicago style offers a footnote/endnote system as an alternative. Instead of parentheses, you place a small superscript number at the point in the text where the citation is needed. That number corresponds to a note at the bottom of the page (a footnote) or at the end of the paper (an endnote) containing the full citation details. The first time you cite a source, the footnote includes the complete information. Subsequent references to the same source use a shortened version with just the author’s last name, a brief title, and the page number.
Building Your Reference List
Every in-text citation must have a matching entry in the list at the end of your paper. APA calls this the “References” page. MLA calls it “Works Cited.” Chicago calls it a “Bibliography.” Regardless of the label, the list is alphabetized by the first author’s last name, not by the order sources appear in your text.
Each entry follows a specific template depending on the source type. A journal article requires different information than a book, a website, or a government report. Here’s what a basic book entry looks like in each style:
- APA: Smith, J. A. (2022). Title of the book. Publisher Name.
- MLA: Smith, John A. Title of the Book. Publisher Name, 2022.
- Chicago: Smith, John A. Title of the Book. City: Publisher Name, 2022.
Notice the differences in what gets italicized, where the year goes, and whether a city of publication is included. These small details are exactly what graders check, so use the official manual or a reliable guide like the Purdue Online Writing Lab (OWL) to get the formatting right for each source type you use.
When You Need to Cite
A good rule of thumb: cite any time you use an idea, fact, statistic, image, or argument that originated with someone else. This applies whether you’re quoting their exact words, paraphrasing in your own language, or summarizing a broader argument. Changing the wording does not remove the obligation to cite.
The exception is common knowledge, which is information so widely accepted that it appears without attribution across many sources. A useful benchmark from Purdue OWL: if you can find a claim stated without a source in at least five credible publications, it likely qualifies as common knowledge. “The Earth orbits the Sun” needs no citation. A specific statistic about orbital speed from a NASA study does.
When you’re unsure whether something counts as common knowledge, cite it. An unnecessary citation is a minor formatting issue. A missing citation can be flagged as plagiarism.
Formatting Direct Quotes
When you use an author’s exact words, enclose them in quotation marks and provide a page number (or paragraph number for online sources without pages). Short quotes, generally under 40 words in APA or under four lines in MLA, stay within the body of your paragraph. Longer quotes get set off as a block quote: indented from the left margin, without quotation marks, with the citation placed after the final period.
Always introduce a quote with context. Don’t drop a quoted sentence into a paragraph on its own. Lead into it by naming the author or explaining why the quote matters, then follow it with your own analysis. The quote supports your argument; it doesn’t replace it.
Paraphrasing Without Plagiarizing
Paraphrasing means restating someone else’s idea in your own words and sentence structure. Simply swapping a few synonyms while keeping the original sentence intact is too close to the source and can still count as plagiarism. To paraphrase well, read the original passage, set it aside, and write the idea from memory in your own voice. Then check your version against the original to make sure you haven’t echoed the phrasing. You still need an in-text citation after a paraphrase, since the idea itself belongs to the original author.
Citing Different Source Types
Books and journal articles are straightforward, but papers today pull from a wider range of sources. Each type has its own required elements.
- Websites: Include the author (or organization if no individual is named), the page title, the site name, the publication or last-updated date, and the URL. If no date is available, APA uses “n.d.” for “no date.”
- Journal articles: Include the author, article title, journal name, volume and issue number, page range, and a DOI (a permanent digital link) if one exists. A DOI is more reliable than a URL because it doesn’t change.
- Videos and podcasts: Include the creator’s name, the title of the episode or video, the platform or series name, the date, and a link.
- Government or organizational reports: Use the agency name as the author when no individual is credited.
If you encounter a source that doesn’t fit neatly into any template, identify the closest category and include as much identifying information as possible: who created it, what it’s called, when it was published, and where a reader can find it.
Tools That Help
Citation generators built into Google Scholar, library databases, and tools like Zotero, Mendeley, or EndNote can save significant time. Most library databases include a “Cite” button next to each article that produces a pre-formatted citation in your chosen style. These generators are helpful starting points, but they frequently contain small errors, especially with capitalization, italics, and date formatting. Always compare the output against the official style guide before submitting.
Reference management tools like Zotero and Mendeley go a step further by storing all your sources in one place and automatically generating both in-text citations and your reference list as you write. They integrate with word processors so you can insert citations without leaving your document. If you’re writing a research-heavy paper or working on a thesis, setting up one of these tools early will save hours of manual formatting later.
Final Checks Before Submitting
Before you turn in your paper, run through a quick audit. First, check that every in-text citation has a corresponding entry in your reference list, and that every entry in the reference list is actually cited somewhere in the paper. Second, verify that names and dates match between the in-text citation and the full entry. Third, confirm your reference list is in alphabetical order. Finally, check the hanging indent: in APA, MLA, and Chicago, each reference entry uses a hanging indent where the first line is flush left and subsequent lines are indented half an inch. This small formatting detail signals that you know the style.