Every researcher eventually runs into a source they can't get their hands on. Maybe it's a 1962 dissertation that was never digitized, a journal your library doesn't subscribe to, or a foreign-language monograph with no translation. You've encountered the idea only because another author quoted or summarized it — so can you cite that original source anyway, using the paper in front of you as your window into it?
This is exactly what a secondary citation is for, and every major style guide provides a specific format for it. But secondary citation is also one of the most misused tools in academic writing, because it's often reached for out of convenience rather than genuine necessity. Skipping the trip to find an original source is faster than tracking it down, and a secondary citation can look, at a glance, exactly like a citation to a source you actually read.
This guide explains precisely what a secondary citation is, why it's discouraged as a first resort, the specific circumstances where it's genuinely appropriate, how to format it correctly across APA, MLA, Chicago, and IEEE, and the process for tracking down a primary source instead of relying on someone else's account of it.
What Is a Secondary Citation?
A secondary citation — sometimes called an indirect citation or secondary referencing — occurs when you cite a source that you encountered only through another author's work, rather than reading it yourself. If a 2024 paper by Kowalski describes a 1998 finding by Fenwick, and you cite Fenwick's finding based only on Kowalski's description of it, you're using a secondary citation. You never opened Fenwick's actual paper; everything you know about it came filtered through Kowalski's summary.
This is different from simply citing Kowalski for Kowalski's own argument. It's specifically about attributing a claim, finding, or quotation to its original author (Fenwick) while acknowledging that your actual source of information was someone else's work (Kowalski). Every major style guide has a dedicated format for exactly this situation, typically using language like "as cited in," "qtd. in," or "cited in" to make the chain of custody explicit to the reader.
The format exists precisely because it needs to be visible. A reader encountering "(Fenwick, 1998, as cited in Kowalski, 2024)" immediately understands that you read Kowalski, not Fenwick — which matters, because it tells the reader exactly how much verification has actually happened and where to go if they want to check the original claim themselves.
Secondary Citation vs. Secondary Source: A Crucial Distinction
Students frequently confuse "secondary citation" with "secondary source," but these are different concepts entirely, and mixing them up leads to real formatting and methodology errors. A secondary source is a type of source — a work that analyzes, interprets, or comments on primary material, such as a textbook, a review article, or a biography. Using a secondary source is completely normal; most literature reviews are built substantially on them, and they're fully legitimate to read and cite directly.
A secondary citation, by contrast, describes how you accessed a piece of information — not what kind of source it came from. You can have a secondary citation to either a primary or a secondary source. If you cite a historical document only because a history textbook quoted it, that's a secondary citation to a primary source. If you cite a theory only because a review article summarized it, that's a secondary citation to what is itself already a secondary source.
The distinction that matters for your reference list: "primary vs. secondary source" describes what kind of material you're citing. "Secondary citation" describes whether you actually read that material yourself, or only encountered it secondhand.
Why Secondary Citations Are Generally Discouraged
Nearly every style guide, and most instructors, treat secondary citation as a fallback rather than a default — something to reach for only after a genuine effort to find the original has failed. The reasons come down to a few specific, recurring risks.
Errors Compound Across Generations
If the secondary author misquoted the original, got the year wrong, or overstated what the original actually found, and you cite it without checking, you inherit that error and potentially pass it on to whoever cites you next. Misattributed quotations and inflated claims have been shown to spread this way across dozens of papers, each one trusting the last without going back to the source.
You Can't Verify Context
A finding pulled out of its original context can mean something different than it appears to mean secondhand. A qualifier, a limitation, or a specific condition attached to the original claim is easy for a summarizing author to compress or drop entirely — and without reading the original, you have no way to know it was ever there.
It Signals Incomplete Research
Reviewers, editors, and instructors read a heavy reliance on secondary citation as a sign the literature review wasn't done thoroughly. A reference list with numerous "as cited in" entries suggests the author didn't go to primary sources when they were reasonably available — which raises questions about the rigor of everything else in the paper.
Retraction and Correction Risk
If you never look at the original source, you have no way of knowing whether it's since been corrected, retracted, or superseded by later work. A secondary summary written before a retraction will keep repeating findings that no longer stand, and you'll have no way to catch that without checking the original's current status.
When Secondary Citations Are Genuinely Acceptable
Despite the risks, secondary citation is a legitimate, sanctioned tool in specific circumstances — every style guide provides a format for it precisely because these situations come up regularly in real research.
- The original is out of print and unavailable through your library, interlibrary loan, or any digital archive after a genuine search
- The original is in a language you can't read and no translation exists, so you're relying on a secondary author's translated excerpt or summary
- The original is a historical document — an archival letter, an out-of-circulation manuscript, or a source that exists only in a specific physical archive you can't access
- The original has been formally withdrawn from circulation but its historical influence still needs to be discussed and cited
- Your discussion is specifically about how the secondary author interpreted the original — in which case you genuinely need to cite both, since your point concerns the interpretation itself
What unites these cases is that the barrier to the original is real and not just inconvenient. "I didn't have time to track it down" or "the library didn't have it on the shelf" don't meet this bar in an era of interlibrary loan, institutional repositories, and document delivery services — most instructors and editors expect a genuine, documented attempt before secondary citation is used.
How to Format Secondary Citations by Style
Every major style handles secondary citation with a specific in-text format, and all of them share one rule: only the secondary source — the one you actually read — appears in your final reference list, bibliography, or works cited. The original source is named in the in-text citation but does not get its own full entry, because you're not vouching for details you never verified firsthand.
APA 7th Edition
In-text format
Reference list entry
Only Kowalski appears in the reference list. Fenwick's original never gets its own entry.
MLA 9th Edition
In-text format
Works Cited entry
MLA uses "qtd. in" (quoted in) specifically for quotations; for paraphrased ideas, "cited in" is more common.
Chicago (Notes-Bibliography)
Footnote format
Chicago's notes system accommodates secondary citation naturally, since the note can name both authors in sequence.
IEEE
In-text and reference note
IEEE has no dedicated secondary-citation format; the convention is to name the original author in prose and cite only the secondary source numerically.
Step-by-Step: Tracking Down the Primary Source Instead
Before reaching for a secondary citation, run through this process. Most sources that seem inaccessible at first turn out to be reachable within a day or two.
- 1
Search the exact title in your library catalog and Google Scholar
Many sources assumed to be unavailable have simply never been searched for directly by title.
- 2
Check whether a DOI resolves to the full text
Even older papers frequently have DOIs now. See our guide to verifying a DOI for the exact process.
- 3
Request it through interlibrary loan
Most academic libraries can request a scan or physical copy of nearly anything from another institution, usually within a few days to two weeks.
- 4
Email the author directly
Most researchers are happy to send a PDF of their own paper on request, especially for older work no longer easily findable online.
- 5
Check institutional repositories and preprint servers
Many authors self-archive a version of their published work even when the publisher version sits behind a paywall.
- 6
If it's truly unreachable, use secondary citation — and say so
Format it correctly per your style guide, and if your instructor or editor allows footnoted explanations, briefly note why the original wasn't accessible.
Common Mistakes with Secondary Citations
Listing the original source in the reference list
Only the source you actually read belongs in your bibliography. Adding a full reference-list entry for a source you never opened misrepresents your research and can look like you verified something you didn't.
Dropping the "as cited in" language entirely
Citing "(Fenwick, 1998)" alone, without disclosing that you read this through Kowalski, misrepresents that you consulted the original directly. This is the single most common secondary-citation error.
Using secondary citation as a default, not a fallback
Reaching for "as cited in" because the original wasn't in the first search result, rather than after a genuine attempt to locate it, is the pattern instructors and editors are trained to notice.
Chaining multiple secondary citations together
Citing a source "as cited in" a paper that itself cited it secondhand compounds the uncertainty even further. If you can't find where the secondary author got their information, treat the claim with extra caution.
What Journals and Instructors Typically Require
Policies vary, but a consistent pattern holds across most academic contexts: secondary citation is tolerated in moderation but discouraged as a habit, and many journals cap how much of a reference list can rely on it. Some instructors set an explicit rule — for example, no more than one or two secondary citations permitted in an undergraduate research paper — precisely to push students toward developing primary-source research skills rather than relying on whatever a previous author happened to summarize.
For theses and dissertations, committees typically expect near-zero secondary citation for sources central to the argument, reserving it only for genuinely obscure historical or foreign-language material that supports background context rather than the core claims. Peer reviewers evaluating a manuscript for publication will often flag heavy secondary citation as a revision request, asking the author to locate and verify the original sources before acceptance.
The safest default, regardless of context, is to treat secondary citation as something you disclose and justify rather than something you use quietly. If more than a small handful of your citations are secondary, that's usually a sign to go back and do more primary-source retrieval before submission.
Frequently Asked Questions
What is a secondary citation?
A secondary citation references a source you learned about through another author's work rather than reading directly — for example, citing a study by Smith because you read about it in a paper by Jones, without having read Smith's original paper yourself.
Is it OK to cite a source I haven't read?
Generally no, not without disclosure. Most style guides and instructors expect you to locate and read the original source whenever possible. Secondary citation using "as cited in" phrasing is reserved for cases where the original is genuinely unobtainable — out of print, in an inaccessible language, or historically impossible to locate.
How do you format a secondary citation in APA?
APA 7th edition format is: (Original Author, Original Year, as cited in Secondary Author, Secondary Year). Only the secondary source — the one you actually read — appears in your reference list; the original source does not get its own entry.
Does a reference checker catch improperly used secondary citations?
A reference checker can flag when a cited source can't be verified or resolved through standard databases, which is often the first sign that a citation is secondary or unverified rather than something you consulted directly. It can't tell you whether disclosure was appropriately included — that's a manual check.
What's the difference between "qtd. in" and "cited in"?
In MLA style, "qtd. in" (quoted in) is used specifically when you're reproducing the original author's exact words as quoted by the secondary source. "Cited in" is the more general phrasing used when you're paraphrasing the original idea rather than quoting it directly.
Conclusion
Secondary citation exists because some sources really are out of reach, and every major style guide gives you a legitimate, well-defined way to handle that situation honestly. The problem isn't the tool itself — it's using it as a shortcut rather than a last resort, and failing to disclose when you've done so.
Before you write "as cited in," take the extra step: search the title directly, check for a DOI, try interlibrary loan, or simply email the author. Most sources that feel unreachable turn out to be a few days away. When a source genuinely can't be found, format the secondary citation correctly, keep only the source you actually read in your reference list, and let the disclosure do its job — telling your reader exactly how far your verification really went.
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