To document a secondary source, you must acknowledge both the original author of the idea and the secondary author whose work you actually read, following the specific "as cited in" rules of your chosen style guide.
A secondary source citation is necessary when you want to use a quote, finding, or idea from an original text (Source A) that you discovered within another author's work (Source B). While the golden rule of academic research is to always track down and read the primary source, this isn't always possible. The original paper might be out of print, written in a language you don't speak, or locked behind an inaccessible paywall. When that happens, you must properly document the secondary source to maintain academic integrity and avoid misrepresenting what you have actually read.
The Golden Rule of Secondary Citations
The most important rule to remember across almost all formatting styles is this: your reference list should only include the source you actually read. You will mention the original author in your text, but the bibliography entry will solely belong to the secondary author.
How to Format Secondary Sources by Style
APA Style
In APA format, you name the original author in your sentence, but your parenthetical in-text citation directs the reader to the secondary source using the phrase "as cited in."
- In-text example: Smith argued that the data was flawed (as cited in Johnson, 2022, p. 45).
- Reference list: Only include the full citation for Johnson's 2022 paper. Do not include Smith.
MLA Style
MLA formatting handles secondary sources similarly but uses the abbreviation "qtd. in" (quoted in) for the in-text citation.
- In-text example: Smith's original study found a "significant drop in engagement" (qtd. in Johnson 45).
- Works Cited: Only create an entry for Johnson's book or article.
Chicago Style
If you are using Chicago Style footnotes or endnotes, you should provide the details of the original author and publication (if known), followed by the phrase "quoted in," and then the publication details of the secondary source.
Best Practices for Researchers
Managing layered references can get messy, especially when you are juggling dozens of PDFs and trying to avoid referencing incorrect or hallucinated sources. To keep your bibliography accurate, WisPaper's TrueCite automatically finds and verifies your citations, ensuring your reference list perfectly matches the secondary texts you consulted.
When writing your literature review, use secondary sources sparingly. Over-relying on them can signal to peer reviewers that you haven't done a thorough literature search. Always make a genuine effort to locate the primary document first, and only fall back on secondary documentation when the original is truly out of reach.
