How to Cite Secondary Sources (As Cited In)

You're reading a textbook by Johnson, and Johnson quotes a study by Martinez that sounds perfect for your paper. You want to cite Martinez, but you haven't actually read Martinez's original work. What do you do?

This is a secondary source situation, and every major citation style has rules for handling it. Getting it wrong can look like academic dishonesty -- you're claiming to have read something you haven't. Getting it right is straightforward once you understand the format.

Primary vs. Secondary Sources

A primary source is the original work you read directly. If you download a journal article by Martinez and cite it, Martinez is your primary source.

A secondary source is a work you learn about through someone else's writing. If Johnson's textbook mentions Martinez's findings and you cite those findings, Martinez is the original source and Johnson is the secondary source -- the one you actually read.

The distinction matters because:

• Accuracy: Johnson may have summarized or interpreted Martinez's findings. Without reading the original, you can't verify accuracy.
• Context: The original study may have important caveats that Johnson didn't mention.
• Honesty: Citing Martinez directly implies you read Martinez. If you didn't, that's misleading.

When Is It Acceptable to Use a Secondary Source?

Secondary citations are meant to be the exception, not the rule. Use them only when:

1. The original source is truly unavailable. It's out of print, behind a paywall you can't access through your library, written in a language you don't read, or from an archive that's not digitized.
2. The original source is a personal communication or unpublished work referenced by the secondary author that you have no way to obtain.
3. The claim is minor to your argument. If Martinez's finding is central to your thesis, you should track down the original. If it's supporting background, a secondary citation may be acceptable.

When you can find the original, always cite it directly. Most journal articles are available through your university library, interlibrary loan, or by emailing the author. DOIs make this easier than ever -- paste a DOI into CiteTools.io and you'll get the full citation instantly.

APA 7th Edition

APA calls these secondary sources and uses the phrase "as cited in."

In-Text Citation

You name the original author in the text and use "as cited in" to credit the source you actually read:

Parenthetical:

Martinez's study found a 40% improvement in retention (as cited in Johnson, 2024).

Narrative:

According to Martinez (as cited in Johnson, 2024), retention improved by 40%.

Reference List

Only the source you actually read goes in the reference list. In this case, Johnson:

Johnson, R. T. (2024). Educational psychology: Theory and practice (8th ed.). Pearson.

Martinez does not appear in your reference list because you didn't read Martinez's work. This is the key difference from a normal citation -- the reference list only contains what you consulted directly.

APA Notes

• Include the year of the original work if known: "Martinez (2019, as cited in Johnson, 2024)"
• APA strongly discourages secondary citations. Their manual explicitly says to find the original whenever possible.
• If you use several secondary citations, an instructor may question whether you've done sufficient research.

MLA 9th Edition

MLA doesn't have a dedicated secondary source format the way APA does, but the approach is similar: acknowledge both sources.

In-Text Citation

Name the original author in your sentence and use "qtd. in" (quoted in) for the parenthetical:

Martinez argues that "spaced repetition increases long-term retention by up to 40%" (qtd. in Johnson 112).

For paraphrased material, you can write it out more naturally:

According to Martinez, spaced repetition significantly improves retention (qtd. in Johnson 112).

Works Cited

Only the source you actually read appears in the Works Cited:

Johnson, Rachel T. Educational Psychology: Theory and Practice. 8th ed., Pearson, 2024.

MLA Notes

• MLA uses "qtd. in" specifically for direct quotations, but you can use the same construction for paraphrased ideas.
• If you're paraphrasing rather than quoting, some instructors accept a narrative approach: "Johnson cites Martinez's finding that..." with only Johnson in the parenthetical.
• When in doubt, use "qtd. in" -- it's the safest format.

Chicago 17th Edition

Chicago handles secondary sources differently depending on whether you're using the notes-bibliography system or the author-date system.

Notes-Bibliography System

In the footnote, cite the original work first, then add "quoted in" or "cited in" with the secondary source:

1. Miguel Martinez, "Spaced Repetition and Memory," Learning Science Quarterly 12, no. 2 (2019): 88, quoted in Rachel T. Johnson, Educational Psychology: Theory and Practice, 8th ed. (New York: Pearson, 2024), 112.

In the bibliography, list the source you actually consulted:

Johnson, Rachel T. Educational Psychology: Theory and Practice. 8th ed. New York: Pearson, 2024.

You may optionally include the original source in the bibliography as well, especially if it's important to your argument.

Author-Date System

Similar to APA, name the original and use "cited in":

(Martinez 2019, cited in Johnson 2024, 112)

The reference list includes only Johnson (or both, if desired).

Chicago Notes

• Chicago gives you the most flexibility. You can include both works in the bibliography if the original source provides useful context for your readers.
• In the footnote, provide as much detail about the original work as the secondary source gives you.

Harvard Style

Harvard uses "cited in" similarly to APA:

In-Text

Martinez (2019, cited in Johnson, 2024) found that retention improved by 40%.

Or:

Retention improved by 40% (Martinez, 2019, cited in Johnson, 2024).

Reference List

Only the secondary source (Johnson) appears in the reference list.

For more on Harvard formatting, see our Harvard referencing guide.

IEEE and Vancouver

Numbered citation styles handle secondary sources less gracefully because the in-text markers are just numbers.

IEEE

Use a footnote or parenthetical note alongside the numbered citation:

Martinez as cited in 5 reported a 40% improvement in retention.

Where 5 is Johnson's entry in your numbered reference list. Only Johnson appears in the reference list.

Vancouver

Similar to IEEE:

Martinez (as cited in Johnson 5) reported improved retention.

In practice, many IEEE and Vancouver users avoid secondary citations entirely by tracking down the original -- these styles are common in STEM fields where most sources are accessible through digital databases. Our IEEE citation guide covers the standard formatting rules.

Common Mistakes

1. Listing the original source in the reference list. If you didn't read Martinez, Martinez shouldn't appear in your References or Works Cited (with the exception of Chicago, which allows it optionally). Including a source you didn't read is a form of misrepresentation.
2. Citing the original source as if you read it. Writing "(Martinez, 2019)" without "as cited in" implies you read Martinez's paper directly. If your instructor checks and the claim doesn't match what Martinez wrote, you have a credibility problem.
3. Overusing secondary sources. One or two secondary citations in a paper is fine. If half your citations are "as cited in," it signals that you haven't engaged deeply with the literature. Most graders notice this.
4. Forgetting to include the original author's name. Writing just "(as cited in Johnson, 2024)" without mentioning Martinez gives Johnson credit for Martinez's work. Always name the original author.
5. Using secondary citations for easily accessible sources. If the original is a journal article with a DOI, there's no excuse for not reading it. Use your library's database, interlibrary loan, or paste the DOI into a citation tool to find it.
6. Getting the "as cited in" / "qtd. in" phrasing wrong. Each style has its own specific wording. Don't mix them -- "qtd. in" is MLA only, "as cited in" is APA and Harvard.

When to Track Down the Original

As a rule, always try to find the original before resorting to a secondary citation. Here's a quick workflow:

1. Check the secondary source's reference list. Find Martinez's full citation in Johnson's bibliography.
2. Search by DOI. If the reference includes a DOI, paste it into your browser or into CiteTools.io for instant access.
3. Search your library database. Use the title and author to search Google Scholar, your university library, or PubMed.
4. Try interlibrary loan. Most universities provide free interlibrary loan that delivers articles within a few days.
5. Email the author. Researchers frequently share their papers when asked. A polite email with your institutional address usually works.

If you've exhausted these options and still can't access the original, a secondary citation is justified.

Quick Reference Table

Try It with CiteTools

When you do track down the original source, formatting its citation is easy. Paste the DOI, URL, or ISBN into CiteTools.io and get the reference in APA, MLA, Chicago, Harvard, IEEE, or Vancouver instantly. No manual formatting, no second-guessing the punctuation. If you're working across multiple styles, you can convert between them with one click.