A research paper is built from other people's work and your own thinking about it. Citing is how you show which is which, and it is how you avoid plagiarism. It looks fussy the first time, with its brackets and full stops, but the idea underneath is simple.
You do two things for every source. You put a short signpost in your sentence where you used the source, and you put the source's full details in a list at the end. The signpost leads the reader to the list, and the list leads the reader to the source. How the two should look is decided by the style your teacher names.
Everything below comes from the two style organisations themselves, the American Psychological Association and the Modern Language Association. Where they disagree, this guide says so. The fiddly half, turning a source into a correctly formatted entry, is the half a tool can take off your hands: EdCitation's free Cite a source looks each source up in the publisher's record and builds the entry, while the reading and every sentence of the paper stay yours.
Why do I have to cite sources?
You cite sources to give credit to the people whose work you used, and to let your reader find that work and check it. Citations also show your own effort: the reader can see how much you read.
The APA describes plagiarism as presenting the words, ideas or images of another person as your own, and the MLA defines it in nearly the same way. Notice the word "ideas": using someone's idea or finding without saying where it came from counts, even when every word is yours.
There is a comforting detail that most students are never told. The American Psychological Association (n.d.) says that a small mistake in a citation, such as a misspelled author name or a missing element, is usually not treated as plagiarism, because it is an oversight rather than an attempt to take credit. It may still cost you marks. So the goal is care, not fear.
What needs a citation, and what is common knowledge?
Anything you took from a source needs a citation, whether you quoted it or put it in your own words. Facts that are common knowledge do not.
| Cite it | No citation needed |
|---|---|
| Someone's exact words, in quotation marks | Your own ideas, opinions and conclusions |
| An idea or explanation you read, put in your own words | Facts most people know, such as the year the Second World War ended |
| Numbers, statistics and results | Your own experiment, survey or observation |
| A picture, chart, table or map you did not make | A book or film you only mention in passing |
| A definition you copied from a dictionary or website | A famous person's dates, found in any reference book |
| A fact you found in one source and nowhere else | Something your teacher taught the whole class |
Two quick tests
Did you know it before you started your research? Could you find it stated in several general sources? If either answer is no, cite it. When you are unsure, cite it. An extra citation does far less harm than a missing one.
Common knowledge is not a fixed list, and the MLA says so plainly: what counts depends on who is reading. Something everybody in your class knows may need a citation for a reader outside your school. If your teacher and your textbook disagree about a particular fact, follow your teacher.
The hard cases
- A source with no author. Start with the title instead, and use a short form of the title in your sentence.
- A source with no date. In APA, write n.d. where the year would go. In MLA, leave the date out.
- A quotation you found inside another book. Read the original if you can. If you cannot, say where you actually read it, and be honest about it.
- A picture or video. These need citations too, even when they were free to use.
- A paper you wrote for another class. Handing the same work in twice can break your school's rules. The APA notes that many institutions treat it that way. Ask before you reuse your own work.
- An AI chatbot. See the fifth mistake below.
How to put a source into your own words properly is covered in Paraphrase, quote or summarise.
What are the two parts of a citation?
Every citation has two parts: a short in-text citation in your sentence, and a full entry in the list at the end. The first words of the list entry match the words in the in-text citation, which is how the reader gets from one to the other.
Here is one book in both styles. APA adds the page number only for a quotation.
| MLA 9 | APA 7 | |
|---|---|---|
| In your sentence | (Sapolsky 45) | (Sapolsky, 2017, p. 45) |
| Name of the list | Works Cited | References |
| Entry in the list | Sapolsky, Robert M. Behave: The Biology of Humans at Our Best and Worst. Penguin Books, 2017. | Sapolsky, R. M. (2017). Behave: The biology of humans at our best and worst. Penguin Books. |
Look closely at the differences. MLA gives the author's full first name and capitalises the main words of the title. APA gives initials and capitalises only the first word, the first word after a colon, and names. MLA puts the year at the end; APA puts it in brackets near the front.
One small rule saves a lot of trouble with books: the year you use is the copyright year printed inside the book, on the page behind the title page, not the year it was reprinted or the year you bought it.
The two parts always travel together. A citation with nothing matching it in the list is broken, and so is a list entry that no sentence points to.
Which citation style does my teacher want, MLA or APA?
Use the style named on your assignment sheet, and if it names none, ask your teacher before you start. In secondary school, which is called high school in the United States, the choice is usually between MLA, common in English and other humanities classes, and APA, common in science and social science classes.
If the assignment sheet runs to several pages, paste it into Check your paper on EdCitation, which is free and needs no account. It reads the instructions into a checklist, with the citation style as one line of it, next to the word limit, the number of sources, and the font and spacing, and each line shows the sentence of the sheet it came from, so you can see the teacher really asked for it.
The two differ in what they put in the sentence. MLA gives the author and the page number, with no comma between them. APA gives the author and the year, with a comma. MLA also builds every entry from the same short list of facts and calls the larger work that holds your source its "container": a short story sits inside an anthology, and an article sits inside a magazine.
Ask which edition as well. The Modern Language Association of America (2021) published the ninth edition of its handbook, which rewrote the explanation of in-text citations, and guides to the eighth edition are still easy to find online. The current APA edition is the seventh (American Psychological Association, 2020).
For the full rules, see the MLA 9 Works Cited guide and APA 7 in-text citations. The main styles are compared in APA vs MLA vs Chicago.
How do I keep track of sources while I read?
Write down the details of each source the moment you first open it, before you take a single note from it. Finding a web page again from memory, the night before the deadline, is the hard way.
If you have not found your sources yet, Find sources on EdCitation searches about 300 million published works by topic, and its filters narrow the results to the kind of source and the range of years your teacher allows.
- Keep one sources file, with one entry for each source, and nothing else in it.
- Record the basics straight away: author, title, website or publisher, date, and the web address or DOI. For a book, add the copyright year and the page numbers you used. Quicker still, build the entry in Cite a source the moment you open the source and paste it in; a free EdCitation account can keep those entries as a reference list in the dashboard instead, each one tagged by topic or by the section of the paper it supports.
- Put the author's name and the page number beside every note as you write the note, not afterwards.
- Put quotation marks round copied words. Later you will not remember which words were yours, and that is how accidental plagiarism happens.
- Write your own thoughts in a different colour, so you can tell your ideas from the source's.
- Save the page as a PDF if it looks like it might change or disappear.
- Tick each source off when its entry is in your final list.
What does a cited paragraph look like?
A cited paragraph has your own point, the information from the source with its in-text citation, and a matching entry in the list at the end. This example is in MLA style and uses a real page from NASA's website, which names no author.
In the paper:
Weather and climate are not the same thing. Weather is what happens this week, while climate change means that the typical weather of a region, or of the whole planet, shifts over many years ("What Is Climate Change?"). This is why one cold winter does not show that the planet has stopped warming.
In the Works Cited list:
"What Is Climate Change?" NASA Science, 21 Oct. 2024, science.nasa.gov/climate-change/what-is-climate-change/.
The first and last sentences are the student's own thinking, so they carry no citation. The middle sentence puts NASA's definition into the student's own words, and it is still cited, because the idea came from the source. The page names no author, so the citation uses the title, which is also how the list entry begins. A web page has no page numbers, so none is given.
The same idea in APA, with a journal article
Chatbots do not look their references up, which is why so many of them are wrong. Walters and Wilder (2023) checked 636 references that ChatGPT produced and found that 55% of those from the older version did not exist at all.
In the References list:
Walters, W. H., & Wilder, E. I. (2023). Fabrication and errors in the bibliographic citations generated by ChatGPT. Scientific Reports, 13, Article 14045. https://doi.org/10.1038/s41598-023-41032-5
Notice that the authors' names are in the sentence, so only the year goes in brackets. That is called a narrative citation, and it is useful when the researchers themselves matter to your point.
One more thing APA asks for that surprises people: do not repeat the same citation in every sentence. When you spend a paragraph on one source, cite it in the first sentence where it belongs and leave the rest clean, as long as it stays obvious which source you mean.
Which five citation mistakes cost the most marks?
The five are citing only quotations, citations and list entries that do not match, a bare web address, mixed styles, and sources you never read.
- Citing only the quotations. Ideas and facts in your own words need a citation too. Fix: ask of each paragraph where its facts came from.
- A citation with no list entry, or a list entry with no citation. Fix: when you finish, tick off each list entry as you find its citation in the paper, or upload the finished paper to Verify references, free, which matches every in-text citation to the list and every entry back to the text.
- A web address standing in for a reference. A pasted link is not a citation, and a search engine is not a source. Fix: give the author, title, website, date and address, in your style's order. Cite a source accepts the address itself, reads the page's details, and lets you correct them before it builds the entry.
- Mixing two styles. An APA year inside an MLA citation, or a list headed "Bibliography" in an APA paper. Fix: check the list's heading and one citation against a guide to your style.
- Listing sources you did not read. This includes references suggested by an AI chatbot, which can look perfect and not exist. Fix: list only what you opened and read, and run any reference a chatbot handed you through Verify references before it goes near your list: each one comes back verified, marked "check this", or not found. See Why AI tools invent references.
How do I build the list at the end?
Build each entry from the source's real details, in the order your style asks for, and put the entries in alphabetical order by the author's surname. You can type each one from your sources file, following a guide, or have it built for you.
Cite a source on EdCitation is the best tool for this, because of where its details come from. It takes a DOI, a title, a PubMed ID, an ISBN (the number printed by the barcode on a book) or a web address, looks the work up in the publisher's record, screens it for retraction, and builds the reference in MLA 9, APA 7 or four other styles, so the details are the publisher's and not your typing. A chatbot cannot do that: it writes a reference that looks right, which is how 55% of the older ChatGPT's references in Walters and Wilder's (2023) test pointed to nothing. Cite a source, Find sources, Verify references and Check your paper are free with no account. Pro ($8 a month) adds tools for longer work, such as checking a paper for plagiarism, and Max ($24 a month) adds the Library of books. EdCitation never writes any part of a paper.
| What you have | What to give Cite a source | What to check in the entry |
|---|---|---|
| A journal article | Its DOI, from the first page | The authors' initials and the year |
| A book | The ISBN, from the back cover | The copyright year, not a reprint year |
| A web page | The web address | The author, or the title if there is none, and the page's own date |
| A reference a chatbot gave you | Nothing yet: verify it first | That it exists, and says what you claim |
In APA, Cite a source sets a title the publisher lists in title case in sentence case, as APA 7 asks, and keeps names and initialisms; glance at any name made of ordinary words.
Either way, read each entry against the source before you hand in. The author, the title and the year should match what the source itself says.
Quick questions
Do I have to cite if I put it in my own words?
Yes. Putting a source's idea into your own words is called paraphrasing, and a paraphrase needs a citation just as a quotation does. Only the quotation marks are dropped, not the citation.
How many sources does a first research paper need?
Neither MLA nor APA sets a number. Check your assignment sheet for a minimum, and ask your teacher if it gives none; EdCitation's Check your paper picks out the number, and any limit on how recent the sources must be, when the sheet sets one.
Do my sources have to be recent?
Not automatically. APA says there is no timeliness rule in its style, so a 1950s paper can be the right source if it is the right source. Some teachers do set a date limit for a particular assignment, and that instruction wins.
Can I cite Wikipedia?
Ask your teacher, because the answer differs from class to class. Wikipedia is useful for getting to know a topic and for the sources listed at the bottom of each article, which you can read and cite yourself.
What if my source has no author?
Start the list entry with the title, and use the title, shortened if it is long, in your in-text citation. In APA the year follows the title. If an organisation published the page, APA treats the organisation as the author.
References
- American Psychological Association. (n.d.). Plagiarism. APA Style. https://apastyle.apa.org/style-grammar-guidelines/citations/plagiarism
- American Psychological Association. (2020). Publication manual of the American Psychological Association (7th ed.). https://doi.org/10.1037/0000165-000
- Modern Language Association of America. (n.d.). Works cited: A quick guide. MLA Style Center. https://style.mla.org/works-cited/works-cited-a-quick-guide/
- Modern Language Association of America. (2021). What's new in the ninth edition of the MLA Handbook (Spring 2021). MLA Style Center. https://style.mla.org/ninth-edition-whats-new/
- National Aeronautics and Space Administration. (2024, October 21). What is climate change? NASA Science. https://science.nasa.gov/climate-change/what-is-climate-change/
- Walters, W. H., & Wilder, E. I. (2023). Fabrication and errors in the bibliographic citations generated by ChatGPT. Scientific Reports, 13, Article 14045. https://doi.org/10.1038/s41598-023-41032-5