What Is Secondary Citation, and When Is It Acceptable?

You Need to Cite an Original Source You Have Not Actually Read

You are reading a paper when the authors describe an earlier study that seems directly relevant to your research. You search for the original but cannot obtain it. Perhaps it is old, unavailable through your library, not digitized, or otherwise inaccessible.

You still want to discuss what the earlier researcher reportedly found. How can you do that without making it look as though you personally read the original?

This is where secondary citation becomes useful. Instead of hiding the intermediary, secondary citation explicitly shows that the information originated in one source but reached you through another source that you actually consulted.

It is a legitimate citation mechanism recognized by major citation systems, but it is generally intended for situations in which consulting the original is genuinely difficult or impossible, not simply inconvenient.

Secondary Citation Makes the Intermediary Visible

How Secondary Citation Preserves the Chain of Evidence

Secondary citation is about how information reached you

Imagine that Researcher A published an influential study in 1985. Researcher B discussed that study in a book published in 2020. You read Researcher B's book but cannot obtain Researcher A's original work.

The intellectual origin of the idea may be Researcher A, but the evidence available to you is Researcher B's representation of Researcher A.

Secondary citation preserves both facts.

The terminology can occasionally be confusing because "primary source" and "secondary source" also have discipline-specific methodological meanings. A historical document, review article, empirical study, or theoretical book can occupy different classifications depending on the research question. In citation practice, the immediate issue is simpler: did you consult the original work, or did you encounter it through another work?

What does "as cited in" actually mean?

In APA-style secondary citation, "as cited in" signals that the original work was not consulted directly. Guidance based on Section 8.6 of the seventh edition of the APA Publication Manual instructs writers to identify the original source in the text and then identify the secondary source after "as cited in." Only the secondary source actually consulted is included in the reference list.

Suppose, hypothetically, that Cruz published a study in 1998 and you know about it only because Reyes discussed it in a 2024 article. An APA-style secondary citation would follow this logic:

Cruz (1998, as cited in Reyes, 2024) reported...

Or parenthetically:

(Cruz, 1998, as cited in Reyes, 2024)

Under this convention, Reyes is the source you actually read and therefore the work that appears in your reference list.

The example names and dates here are hypothetical. The point is the structure: original source first, source actually consulted second.

Secondary citation is not unique to APA

Other citation systems recognize the same underlying problem but express it differently.

MLA uses qtd. in, meaning "quoted in," for indirect quotations. Its official Style Center shows that the original author's name can appear in the prose, citation, or note, while the Works Cited entry corresponds to the source actually consulted.

Chicago also recognizes citation through a secondary source. Its official guidance says that this practice is generally discouraged because authors are expected to examine the works they cite, but when the original is unavailable it provides a "quoted in" construction identifying both the original and the secondary source.

Do not treat these expressions as interchangeable formatting templates. Citation styles differ in punctuation, reference-list or bibliography treatment, locators, and how quotations and paraphrases are handled. Follow the current edition and system required by your institution, journal, supervisor, or publisher.

Why is finding the original usually better?

Because a secondary source places another researcher between you and the evidence.

The intermediary may summarize the original accurately. But they may also omit context, simplify the method, emphasize one finding over another, reproduce a bibliographic error, or interpret the original through the concerns of their own argument.

If you obtain the original, you can determine what it actually says rather than relying on someone else's representation.

This is why guidance on secondary citation commonly recommends locating the original whenever possible. APA-oriented guidance advises using secondary sources sparingly and finding the primary source when possible. Chicago goes further in explicitly describing secondary-source citation as generally discouraged when the original can be examined.

A paywall does not automatically justify secondary citation

Suppose the original article is available on the publisher website but requires payment. You already have a later paper describing it. Is "as cited in" now justified?

Not necessarily.

A paywall closes one access route, not every access route. Before falling back on a secondary citation, check institutional subscriptions and the other legitimate options for accessing a research paper behind a paywall.

You may be able to find a legal open-access version, obtain the paper through your library, or request a copy directly from the author.

If the original is important to your argument, a few additional retrieval steps are usually preferable to relying on another author's interpretation.

When can secondary citation be reasonable?

There is no universal threshold at which an original becomes "inaccessible enough." Still, several circumstances can make secondary citation defensible.

The original may be out of print and unavailable through accessible collections. It may be an archival or historical source that you cannot reasonably obtain. A work may be cited from an edition or document that is no longer retrievable. In some cases, the original may be available only in a language the researcher cannot read adequately, although translation and specialist assistance should be considered when the source is important.

APA-oriented university guidance explicitly gives examples such as an original being out of print, unavailable, or available only in a language the writer does not understand.

The common feature is genuine inability to consult the original, rather than a preference not to look for it.

Convenience alone is a weak justification

"The original would take another five minutes to find" is not much of an access barrier.

Nor is "the review already summarized it nicely."

If the original is readily available, reading it lets you verify both the claim and the citation. This is particularly important when the source is central to your argument, provides a key numerical result, supports a methodological choice, or is being quoted directly.

Secondary citation should reduce an unavoidable evidential limitation, not create one unnecessarily.

The importance of the claim should influence how hard you try

Retrieval effort should be proportionate to evidential importance.

If an inaccessible nineteenth-century text provides a minor historical illustration, a secondary citation may be entirely reasonable. If an inaccessible empirical paper supposedly provides the principal evidence for your study's theoretical claim, relying on someone else's one-sentence summary is considerably harder to defend.

The more weight you place on the original source, the stronger the reason to locate it.

If you already have its bibliographic details but not the document, work systematically through the options available when you can find the citation but not the full text.

Secondary citation applies to paraphrases as well as quotations

The issue is not limited to quotation marks.

Suppose Reyes paraphrases Cruz, and you paraphrase Reyes's description of Cruz. You still have not read Cruz.

Changing the wording does not change the route through which the information reached you. MLA's Style Center explicitly addresses indirect-source situations beyond simply reproducing a quotation, and APA secondary-source guidance applies when information from an original source is known through a work actually consulted.

The relevant question is therefore not "Did I quote the original?" It is "Did I consult the original?"

Do not put the unread original in your references as though you consulted it

This is one of the most consequential mistakes secondary citation is designed to prevent.

Under APA's secondary-source convention, the reference list contains the secondary source you actually read, not a separate reference-list entry for the original source you did not consult.

MLA's indirect-source example likewise gives the Works Cited entry for the work actually consulted.

Chicago requires attention to which of its citation systems you are using. Its official FAQ shows both the original and secondary source in the note for an unavailable original, while Chicago-based guidance commonly places the consulted secondary source in the bibliography.

Do not import APA's reference-list rule mechanically into MLA or Chicago. The underlying principle is shared, but implementation is style-specific.

Secondary citation is not the same as citing a secondary source normally

The terminology can produce another misunderstanding.

A literature review is commonly described as a secondary source because it synthesizes previous research. If you cite that review for its own synthesis, argument, classification, or interpretation, you are simply citing a source you read. No "as cited in" construction is necessary.

Secondary citation arises when you use that review as the intermediary for a different work that you did not read.

Secondary citation does not verify the original claim

Using "as cited in" is an act of transparency. It is not an independent validation of the original evidence.

You still do not know whether the intermediary summarized the original perfectly. That limitation should affect how strongly you rely on the claim.

If the statement is contentious, highly specific, numerical, methodological, or central to your argument, consider whether it would be better to omit it if the original cannot be checked.

Sometimes the most rigorous response to an inaccessible source is not a more elaborate citation. It is deciding that the claim does not have enough evidential support to carry the weight you intended to place on it.

If you later obtain the original, the situation changes

Suppose you initially wrote a secondary citation because the original was unavailable. Later, your library obtains the paper.

Read the relevant material and verify the claim. If the original supports what you wrote, you can normally replace the secondary citation with a direct citation to the original.

You may discover that the intermediary described it accurately. You may also discover a qualification that changes your sentence.

Once you have personally consulted the original, there is no reason to preserve "as cited in" merely because another paper first helped you discover it.

Reading only the original abstract creates a different problem

If you locate the original article but can access only its abstract, you have directly consulted part of the original publication rather than knowing it entirely through another source.

You may be able to use that abstract for a limited claim that it explicitly supports. But you should not use details from the secondary source as though you verified them in the original.

In that situation, consider separately whether citing the paper after reading only its abstract is defensible for the particular claim.

When "As Cited In" Is Appropriate and When It Is Not

The deciding factor is not the age of the source or the existence of another paper that cites it. The question is whether you can reasonably consult the original and how much evidential weight the claim carries in your own work.

Common Misunderstandings About Secondary Citation

Treat Secondary Citation as a Transparent Fallback

The strongest practical rule is not "never use secondary citations." It is "do not use them when you can reasonably verify the original yourself."

Secondary citation is therefore best understood as an honesty mechanism. It lets you use information when the original is genuinely beyond reach without pretending that your evidential access was better than it actually was.

Before Using a Secondary Citation, Check These Points

Questions About Secondary and Indirect Citation

Secondary Citation Is Useful Because It Does Not Pretend You Read the Original

How to Cite This Guide

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