Citing a source in a paper requires two things: a short reference where you use the information (called an in-text citation) and a full entry in a list at the end of your paper. The exact format depends on the citation style your instructor or publisher requires, with APA, MLA, and Chicago being the most common. Once you understand the basic pattern, citing any source follows the same logic.
When You Need a Citation
Any time you use someone else’s ideas, data, or words, you need a citation. That includes direct quotes, paraphrased arguments, statistics, charts, and findings from studies. The only exception is common knowledge, which refers to widely accepted facts you could find stated without attribution in at least five credible sources. “Water boils at 100 degrees Celsius” needs no citation. A specific researcher’s finding about boiling points under unusual conditions does.
If you’re unsure whether something counts as common knowledge, cite it. An unnecessary citation is harmless. A missing one can be flagged as plagiarism.
How In-Text Citations Work
An in-text citation is the brief marker you place in your sentence to tell readers where the information came from. It points them to the full reference at the end of your paper. You have two ways to do this: weave the author’s name into your sentence (a narrative citation) or place the reference information in parentheses at the end of the borrowed material (a parenthetical citation).
In APA style, in-text citations follow an author-date format. A parenthetical citation looks like this: (Jones, 1998). If you’re quoting directly, add the page number: (Jones, 1998, p. 199). For a narrative citation, you mention the author by name and put the year in parentheses right after: Jones (1998) found that students struggled with citation formatting. The page number still goes in parentheses at the end of the quote.
MLA uses author-page instead of author-date. A parenthetical citation looks like (Jones 199), with no comma between the name and the page number and no “p.” abbreviation. Chicago style offers two systems: a notes-bibliography system using footnotes or endnotes, and an author-date system similar to APA’s. Your instructor will specify which one to use.
When you paraphrase rather than quote directly, you still need the in-text citation. The only difference is that you don’t use quotation marks and, in APA, the page number is encouraged but not always required for paraphrases.
Building the Reference List
The reference list (called “References” in APA, “Works Cited” in MLA, or “Bibliography” in Chicago) goes on its own page at the end of your paper. Every source you cited in the text gets a full entry here, and every entry here should correspond to an in-text citation. This list gives your reader enough information to find each source themselves.
A few formatting rules apply across all major styles. Arrange entries alphabetically by the first author’s last name. Use a hanging indent, meaning the first line of each entry sits flush left and every subsequent line is indented. Do not number or bullet the entries. Do not group them by type or arrange them in the order they appear in your paper.
Formatting Entries by Style
Each style arranges the same basic pieces of information (author, title, date, publisher or journal, location details) in a slightly different order and with different punctuation. Here’s how the same journal article looks in each style:
- APA: Frank, H. (2011). Wolves, dogs, rearing and reinforcement: Complex interactions underlying species differences in training and problem-solving performance. Behavior Genetics, 41(6), 830–839.
- MLA: Frank, H. “Wolves, Dogs, Rearing and Reinforcement: Complex Interactions Underlying Species Differences in Training and Problem-Solving Performance.” Behavior Genetics 41.6 (2011): 830-39.
- Chicago: Frank, H. 2011. “Wolves, Dogs, Rearing and Reinforcement: Complex Interactions Underlying Species Differences in Training and Problem-Solving Performance.” Behavior Genetics 41 (6): 830–839.
Notice the differences. APA puts the year right after the author and uses sentence case for article titles (only the first word and proper nouns capitalized). MLA places the year near the end and capitalizes all major words. Chicago moves the year after the author but before the title. These details matter because instructors check for consistency, and mixing styles in a single paper is a common way to lose points.
Citing Websites, Videos, and Social Media
Online sources follow the same logic as print sources: identify who created it, when, what it’s called, and where to find it. For a webpage, include the author (or organization if no individual is listed), the date of publication or last update, the title of the page, the name of the website, and the URL. If no date is available, APA uses “n.d.” (no date) in place of the year.
For a YouTube video, the author is typically the channel name, followed by the upload date, the video title, and the URL. Social media posts use the poster’s name or handle as the author, the date of the post, the first portion of the post text as the title (often the first 20 words), and the URL.
Citing AI-Generated Content
If you used a tool like ChatGPT or Gemini in your research, most style guides now have specific rules for citing it. In APA style, the author of an AI-generated response is the company that developed the tool, not the AI itself, because authorship requires a living person who can take responsibility for the content.
When citing a specific AI conversation, the APA reference format is: Company Name. (Year, Month Day). Title of chat [Generative AI chat]. Tool Name. URL of the chat. The date is the day the conversation took place or concluded. If the tool lets you share a link to the chat, include that URL so readers can review the exchange.
When referring to an AI tool in general terms rather than citing a specific conversation, the reference format shifts slightly: Company Name. (Year). Tool Name [Large language model]. URL of the tool. The date here is the year the tool was most recently updated. You should also keep a record of the prompts you used, even if they don’t appear in the reference itself. Some instructors ask you to include prompts in an appendix.
Step-by-Step Process for Any Source
Regardless of style, citing a source follows the same workflow every time. First, record the source details as you research. Trying to track down a URL or publication date after the fact wastes time and leads to incomplete citations. Note the author, title, date, publisher or website, page numbers, and URL while the source is still open in front of you.
Second, determine what type of source it is: journal article, book, website, video, government report, interview, or something else. Each type has its own template in your style guide. Third, plug the details into the correct template for your assigned style. Fourth, create the in-text citation wherever you use material from that source. Finally, double-check that every in-text citation has a matching entry in your reference list and vice versa.
Citation generators built into databases like JSTOR or Google Scholar can give you a head start, but they frequently contain errors in capitalization, italics, or date formatting. Always compare the output against your style guide’s template before pasting it into your paper.
Quick Reference for Common Source Types
The templates below use APA format, since it’s the most widely assigned style in colleges. Swap the order and punctuation for MLA or Chicago by checking your style manual.
- Book: Author, A. A. (Year). Title of work: Capital letter also for subtitle. Publisher.
- Journal article: Author, A. A. (Year). Title of article. Title of Periodical, volume(issue), pages. DOI or URL
- Webpage: Author or Organization. (Year, Month Day). Title of page. Site Name. URL
- YouTube video: Channel Name. (Year, Month Day). Title of video [Video]. YouTube. URL
For sources with two authors, list both names joined by an ampersand in the reference list (Smith, A., & Lee, B.) and use both names in every in-text citation (Smith & Lee, 2022). For three or more authors in APA, list all authors in the reference entry but shorten the in-text citation to the first author’s last name followed by “et al.” (Smith et al., 2022).