Direct answer: A secondary source citation tells readers when you are using a work you encountered through another source rather than reading yourself. Whenever possible, locate and cite the original work. If you cannot, follow your required style: APA uses “as cited in,” MLA uses “qtd. in” for an indirect quotation, and Chicago notes-bibliography uses “quoted in.” Your citation should not suggest you personally consulted the original.

Finding a useful quotation or research claim inside an article can raise a deceptively simple question: do you cite the original author, the article you read, or both? The answer depends on whether you found the original source and which citation style your assignment requires. This guide explains the decision and gives practical APA, MLA, and Chicago examples.

What a secondary source citation means

A secondary source citation—also called an indirect citation or a “source within a source”—is used when you learn about an original work from a source you did read. The original work is the primary source in this citation relationship; the source you consulted is the secondary source.

For example, imagine that a 2020 journal article by Jones describes a 2001 study by Smith. You read Jones’s article, but Smith’s study is unavailable. If you use the finding, you need to signal that your knowledge of Smith’s work comes through Jones. The citation gives credit to the original researcher while also identifying the source you actually consulted.

This distinction matters because a secondary author may summarize, interpret, or quote an original work selectively. Readers need enough information to trace the claim and understand how you encountered it. A transparent citation is more accurate than listing an unread work as though you examined it directly.

When should you find the original source?

Try to locate the original before relying on a secondary source. Search your library catalogue and databases using the author, title, publication year, journal, or DOI given in the source’s reference list. A scholarly search engine, publisher site, or library interlibrary-loan service may help you find a copy. If you locate it, read the relevant passage in context and cite the original according to your style guide.

Use a secondary citation when the original is genuinely unavailable, such as when it is out of print, inaccessible after reasonable searching, or not readable in a language you understand. Your instructor, department, or publisher may set additional rules, so follow those requirements first. APA guidance, for example, recommends using secondary sources sparingly and gives examples for cases where the original work cannot be accessed. See the APA Style guidance on secondary sources.

Consider whether the exact claim is important enough to keep. If the original cannot be checked and the claim is central to your argument, look for another reliable source that supports it directly. If you retain it, make the citation transparent and avoid implying that you verified the original yourself.

How to make a secondary source citation in APA, MLA, and Chicago

Each style communicates the citation chain differently. The examples below use the same illustrative scenario: Smith published a study in 2001, and Jones discussed it in a 2020 article. These names and publication details are examples only; replace them with the information from your actual sources. Always check the assignment’s required edition and any instructor-specific directions.

APA 7: use “as cited in”

In APA, name the original author in your sentence or citation, then write “as cited in” before the author and year of the secondary source you read. For example:

Smith’s findings suggested that sleep duration affected recall (as cited in Jones, 2020).

If you quote wording reproduced in Jones, include the page number for the material in the source you actually consulted when available:

Smith described the result as “a gradual change in recall” (as cited in Jones, 2020, p. 48).

In the reference list, include Jones’s article—the source you read—not Smith’s inaccessible study. If you later access Smith’s original, cite it directly and provide its reference entry instead. For APA examples of the reference-list principle, see Purdue OWL’s APA reference-list guidance.

MLA 9: use “qtd. in” for an indirect quotation

When quoting words by Smith that you encountered in Jones, MLA uses “qtd. in” (short for “quoted in”) to point to the source you consulted. An illustrative parenthetical citation might read:

Smith calls the result “a gradual change in recall” (qtd. in Jones 48).

The Works Cited entry should identify Jones’s article, which is the work you accessed. MLA’s own Style Center explains that the original author’s name may appear in the prose, in the citation, or in a note; its example also uses “qtd. in.” See MLA Style Center’s guidance on citing indirect sources.

Be careful with paraphrases. If you are summarizing Jones’s explanation rather than reproducing Smith’s words, cite Jones as the source of the information you read. Do not use “qtd. in” automatically just because Jones mentions another author. Make the relationship clear in your wording if identifying Smith is relevant to your point.

Chicago 18: “quoted in” for notes-bibliography

Chicago generally discourages citing a work secondhand because writers are expected to examine sources they cite. If an original source is unavailable, the notes-bibliography system allows a note to identify the original and connect it to the secondary source with “quoted in.” For example, an illustrative note could read:

1. Smith, “Study Title,” 22, quoted in Alex Jones, “Article Title,” 48.

In Chicago’s notes-bibliography guidance, when the original is unavailable, both the original and the secondary source are listed in the bibliography. The note should make clear which source you consulted and where the quoted material appears there. Chicago has two documentation systems, so do not assume the notes-bibliography example automatically applies to author-date. Check the system required for your paper and consult the Chicago Manual of Style’s secondary-source example.

A step-by-step workflow for a secondary source citation

1. Identify the source you actually read. Record its author, date, title, and the page or section where it discusses the original work.
2. Record the original source’s details. Use the secondary source’s reference list to note the original author, title, date, and publication details. Do not treat this information as independently verified.
3. Try to access the original. Search your library or a scholarly database. If you find it, check the relevant passage and cite it directly.
4. Decide what you are using. Are you quoting the original author’s exact words as reproduced in the secondary source, or summarizing the secondary author’s explanation? That affects your wording and citation.
5. Apply the required style. Use APA’s “as cited in,” MLA’s “qtd. in” for an indirect quotation, or the appropriate Chicago method. Confirm any edition or course-specific instructions.
6. Build the source-list entry from the work you consulted. Apply the relevant style’s rules for the reference list, Works Cited, or bibliography. Chicago notes-bibliography has its own direction for unavailable originals.
7. Check the citation chain. A reader should be able to tell which work is original, which one you read, and where the cited material appears.

Common mistakes and a final checklist

• Listing an unread source as directly consulted. Do not give readers the impression that you examined an original you did not access.
• Citing only the original author. Without identifying the source you read, the citation hides how you encountered the information.
• Adding “as cited in” or “qtd. in” without checking the style. These phrases are style-specific; they are not interchangeable decorations.
• Confusing a quotation with a paraphrase. Quotation marks are for exact words. A paraphrase uses your own wording but still needs a citation to the source of the information.
• Copying an old reference entry without checking it. A secondary author may reproduce incomplete or incorrect bibliographic details. Verify what you can, and do not invent missing facts.
• Overusing secondhand evidence. Too many indirect citations can make an argument depend heavily on other writers’ summaries. Seek out key original sources where practical.

Before submitting, check:

• Have I tried to locate the original source?
• Does my sentence distinguish the original author’s claim from the secondary author’s interpretation?
• Does my in-text citation name the source I actually read?
• Does the final source list follow my assigned citation style?
• Have I included page or location details when required and available?
• Have I avoided implying that I personally reviewed an inaccessible original?

For a broader process for assessing source credibility, see OakWrites’ guide to evaluating scholarly sources. For related citation situations, read how to cite a source with no author.

Frequently asked questions

What is a secondary source citation?

It is a citation that identifies an original work discussed through another source you read. It makes clear that your access to the original author’s words or ideas came through the secondary source.

Should I cite the original source or the source I read?

Try to find and read the original, then cite it directly. If it is not reasonably available, use the citation format required by your style guide to identify both the original work and the source you consulted. Follow that style’s rules for the reference list or bibliography.

Does APA include the original source in the reference list?

For an APA secondary citation, the reference list includes the source you actually consulted. The in-text citation identifies the original author and uses “as cited in” before the secondary source information.

What does “qtd. in” mean in MLA?

“Qtd. in” means “quoted in.” MLA uses it to show that a quotation attributed to one author was found in another work. The Works Cited entry points readers to the source you consulted.

Can I use a secondary source citation for a paraphrase?

Yes, if the original is unavailable and your style guide allows it. Cite the source you actually read and make the attribution clear. In MLA, reserve “qtd. in” for an indirect quotation; a paraphrase of the secondary author’s explanation should be attributed to that source.

Key takeaways

• Whenever practical, locate and cite the original work directly.
• If you cannot, disclose the citation chain rather than presenting the original as personally consulted.
• APA uses “as cited in”; MLA uses “qtd. in” for an indirect quotation; Chicago notes-bibliography uses “quoted in” when an original is unavailable.
• Reference-list and bibliography rules differ, so use the assigned style and edition rather than mixing formats.

Accurate source attribution depends on both the in-text citation and the final source list working together. If you need help checking citation consistency or formatting, explore OakWrites editing, proofreading, and formatting services. You can also review OakWrites pricing or submit a document for a personalized quote.

Sources: APA Style, Secondary Sources; MLA Style Center, Citing Indirect Sources; The Chicago Manual of Style, Documentation FAQ; Purdue OWL, APA Reference List: Other Print Sources; Purdue OWL, MLA In-Text Citations.