How to Cite Sources in a Research Paper

Proper citation is non-negotiable in academic writing. It gives credit to original authors, allows readers to verify your sources, and protects you from plagiarism.

This guide covers everything you need to know about citing sources, including APA, MLA, and Chicago formats with clear examples.

Why Citations Matter

Academic Integrity

Gives credit to original researchers
Avoids plagiarism (a serious academic offense)
Shows your research is thorough

Credibility

Supports your claims with evidence
Allows verification of your sources
Demonstrates expertise in your field

Reader Value

Enables further reading on topics
Shows the conversation you're joining
Provides context for your arguments

Understanding Citation Components

Every citation has two parts:

1. In-Text Citation

Appears in the body of your paper
Brief reference (author, date, page)
Signals that information came from a source

2. Full Reference

Appears at the end of your paper
Complete publication information
Listed in "References," "Works Cited," or "Bibliography"

Both parts are required—in-text citations point to full references.

APA Format (7th Edition)

Used in: Sciences, psychology, social sciences, education

In-Text Citations

One Author:

Research shows significant effects (Smith, 2024).
Smith (2024) found significant effects.

Two Authors:

(Smith & Jones, 2024)
Smith and Jones (2024) found...

Three or More Authors:

(Smith et al., 2024)
Smith et al. (2024) demonstrated...

Direct Quote:

"Exact words from source" (Smith, 2024, p. 45).
Smith (2024) stated, "exact words" (p. 45).

Multiple Sources:

Several studies confirm this (Jones, 2023; Smith, 2024).

Reference List Format

Journal Article:

Author, A. A., & Author, B. B. (Year). Title of article. Journal Name,
    Volume(Issue), Page–Page. https://doi.org/xxxxx

Example:

Smith, J. A., & Johnson, M. B. (2024). Effects of sleep on memory
    consolidation in adolescents. Journal of Cognitive Neuroscience,
    36(4), 123–145. https://doi.org/10.1162/jocn_a_01234

Book:

Author, A. A. (Year). Title of book: Subtitle. Publisher.

Example:

Johnson, R. T. (2023). Research methods for beginners: A practical
    guide. Academic Press.

Book Chapter:

Author, A. A. (Year). Title of chapter. In E. E. Editor (Ed.), Title
    of book (pp. xx–xx). Publisher.

Website:

Author, A. A. (Year, Month Day). Title of page. Site Name. URL

Example:

Centers for Disease Control. (2024, January 15). Teen mental health.
    CDC. https://www.cdc.gov/teen-mental-health

No Author:

Title of article. (Year). Publication Name. URL

No Date:

Author, A. A. (n.d.). Title. URL

APA Reference List Rules

Title: "References" (centered, bold)
Alphabetical by first author's last name
Double-spaced
Hanging indent (first line flush left, subsequent lines indented 0.5")
DOIs when available

MLA Format (9th Edition)

Used in: Literature, humanities, arts

In-Text Citations

One Author:

Research shows significant effects (Smith 45).
Smith found significant effects (45).

Two Authors:

(Smith and Jones 45)

Three or More Authors:

(Smith et al. 45)

No Page Number:

(Smith)
Smith argues that...

No Author:

("Title of Article" 45)

Multiple Sources:

(Smith 45; Jones 67)

Works Cited Format

Journal Article:

Last, First. "Title of Article." Journal Name, vol. #, no. #, Year,
    pp. #–#.

Example:

Smith, John. "Memory and Learning in Adolescents." Cognitive Psychology
    Quarterly, vol. 42, no. 3, 2024, pp. 234–256.

Book:

Last, First. Title of Book. Publisher, Year.

Example:

Johnson, Rebecca. Research Methods for Students. Academic Press, 2023.

Website:

Last, First. "Title of Page." Website Name, Publisher, Day Month Year,
    URL.

Example:

Smith, John. "Understanding Research Methods." Research Hub, Research
    Foundation, 15 Jan. 2024, www.researchhub.org/methods.

No Author:

"Title of Article." Website Name, Day Month Year, URL.

MLA Works Cited Rules

Title: "Works Cited" (centered)
Alphabetical by first element (usually author's last name)
Double-spaced
Hanging indent
Access date optional for online sources

Chicago Style

Used in: History, some sciences, publishing

Chicago has two systems:

Notes-Bibliography (Humanities)

Uses footnotes/endnotes plus bibliography.

Footnote (First Reference):

1. John Smith, Research Methods (New York: Academic Press, 2024), 45.

Footnote (Subsequent):

2. Smith, Research Methods, 67.

Bibliography:

Smith, John. Research Methods. New York: Academic Press, 2024.

Author-Date (Sciences)

Similar to APA.

In-Text:

(Smith 2024, 45)

Reference List:

Smith, John. 2024. Research Methods. New York: Academic Press.

Quick Reference: Common Source Types

Journal Article

Format	Example
APA	Smith, J. (2024). Title. Journal, 10(2), 45–67. https://doi.org/xxx
MLA	Smith, John. "Title." Journal, vol. 10, no. 2, 2024, pp. 45–67.
Chicago	Smith, John. "Title." Journal 10, no. 2 (2024): 45–67.

Book

Format	Example
APA	Smith, J. (2024). Title of book. Publisher.
MLA	Smith, John. Title of Book. Publisher, 2024.
Chicago	Smith, John. Title of Book. City: Publisher, 2024.

Website

Format	Example
APA	Author. (Year, Month Day). Title. Site. URL
MLA	Author. "Title." Site, Day Month Year, URL.
Chicago	Author. "Title." Site. Accessed Month Day, Year. URL.

Special Cases

No Author

APA:

In-text: ("Title of Article," 2024)
Reference: Title of article. (2024). Publication. URL

MLA:

In-text: ("Title of Article" 45)
Works Cited: "Title of Article." Publication, 2024, pp. 45–50.

No Date

APA:

In-text: (Smith, n.d.)
Reference: Smith, J. (n.d.). Title. URL

MLA:

Works Cited: Smith, John. "Title." Website, URL. Accessed 15 Jan. 2024.

Multiple Works by Same Author

APA (same year):

(Smith, 2024a)
(Smith, 2024b)

MLA:

Use title to differentiate: (Smith, "First Article" 45)

Secondary Sources (Citing a Source Within a Source)

Try to find the original, but if you can't:

APA:

In-text: (Original Author, as cited in Smith, 2024)
Reference: Only list Smith (the source you read)

MLA:

In-text: (qtd. in Smith 45)
Works Cited: Only list Smith

Personal Communication

APA:

In-text: (J. Smith, personal communication, January 15, 2024)
Reference: Not included (can't be retrieved by readers)

Videos and Podcasts

APA:

Author/Creator. (Year, Month Day). Title [Video]. Platform. URL

Example:

TED. (2024, March 1). The science of learning [Video]. YouTube.
    https://www.youtube.com/watch?v=xxxxx

When to Cite

Always Cite:

Direct quotes
Paraphrased ideas from sources
Statistics and data
Specific facts that aren't common knowledge
Others' theories, methods, or frameworks
Images, figures, or tables from sources

Don't Need to Cite:

Common knowledge ("The Earth orbits the Sun")
Your own original ideas and analysis
Your own data and observations
Generally known facts in your field

When in Doubt:

Cite it. Over-citation is better than plagiarism.

Avoiding Plagiarism

What Counts as Plagiarism

Copying text without quotes and citation
Paraphrasing without citation
Using someone's ideas without credit
Self-plagiarism (reusing your own work without disclosure)
Buying or copying someone else's paper

How to Avoid It

1. Take Careful Notes

Mark direct quotes clearly in your notes
Always record source information
Distinguish your ideas from source ideas

2. Paraphrase Properly

Change both words AND sentence structure
Don't just swap synonyms
Still requires citation

3. Quote When Appropriate

Use exact words with quotation marks
Include page number
Don't overuse quotes

Bad Paraphrase (Plagiarism):

Original: "Social media use correlates strongly with anxiety in teens." Bad: "Social media usage correlates significantly with anxiety in teenagers."

Good Paraphrase:

Original: "Social media use correlates strongly with anxiety in teens." Good: Research has found a significant relationship between how much time adolescents spend on social platforms and their reported anxiety levels (Smith, 2024).

Citation Tools

Citation Managers

Zotero (Free)

Saves sources from browser
Generates citations automatically
Works with Word and Google Docs

Mendeley (Free)

Good for PDFs
Social features
Citation generation

EndNote (Paid)

Powerful features
Steep learning curve
Common in academia

Online Generators

Use with Caution:

Citation Machine
EasyBib
BibMe

Warning: Always verify auto-generated citations. They often contain errors.

Best Practice

Use a citation manager to organize
Generate citations with the tool
Always check for accuracy
Format according to your style guide

Common Mistakes

Mistake 1: Inconsistent Format

Problem: Mixing APA and MLA Fix: Choose one style and use it throughout

Mistake 2: Missing Page Numbers for Quotes

Problem: "Direct quote" (Smith, 2024). Fix: "Direct quote" (Smith, 2024, p. 45).

Mistake 3: Wrong Hanging Indent

Problem: Reference list without proper indentation Fix: First line flush left, subsequent lines indented

Mistake 4: Incorrect Author Format

Problem: John Smith (2024) Fix (APA): Smith (2024) or J. Smith (2024)

Mistake 5: Missing DOIs

Problem: Not including DOI when available Fix: Always include DOI for journal articles

Mistake 6: Incorrect Italics

Problem: Wrong elements italicized Fix: Italicize book titles and journal names, not article titles (APA)

Mistake 7: Not Matching In-Text to References

Problem: In-text citation with no matching reference Fix: Every in-text citation needs a full reference (and vice versa)

Checklist Before Submitting

In-Text Citations

Every source has an in-text citation
Format is consistent (APA, MLA, or Chicago)
Direct quotes have page numbers
Multiple authors handled correctly
All in-text citations match reference list

Reference List

Title is correct ("References" for APA, "Works Cited" for MLA)
Alphabetical order by first author
Hanging indent applied
Double-spaced
All required elements included
DOIs included when available
URLs are active and correct
Every reference has an in-text citation

Getting Help

Proper citation takes practice. Expert guidance helps you get it right.

The YRI Fellowship provides:

Writing Support: Feedback on citations and formatting
Multiple Reviews: Catch errors before submission
Publication Guidance: Learn journal-specific requirements
1:1 Mentorship: Experts answer your questions

Apply to YRI Fellowship →

Which citation style should I use? Use what your instructor, competition, or target journal requires. For science fairs, APA is most common for sciences. If not specified, APA is a safe choice for STEM fields.

How do I cite a source I found in another source? Try to find and read the original source. If you can't, use "as cited in" (APA) or "qtd. in" (MLA) and only list the source you actually read in your references.

Do I need to cite common knowledge? No. Facts that are widely known don't need citations. However, if you're unsure whether something counts as common knowledge, cite it.

Can I use citation generators? Yes, but always verify the output. Generators frequently make errors, especially with unusual sources.

How many citations should my paper have? There's no fixed number, but every claim that isn't common knowledge or your own original idea needs a citation. A typical research paper has citations every 1-2 paragraphs.

What if a source has no author or date? Use the organization name as author, or "Anonymous" if truly unknown. Use "n.d." (no date) if no date is available.

How to Cite Sources in a Research Paper (Complete Guide)

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