What is a secondary source in a citation?

It is the work in which you read about another work. The original work is the primary source; the one you actually opened is the secondary source. APA 7 §8.6 defines a secondary source as content first reported in another source. That is a question of access, not of document type, and it is not the historian's primary-versus-secondary test.

How do I write "as cited in" in APA 7?

Name the primary author and year, then the phrase as cited in, then the secondary source in normal author–date form: (Rabbitt, 1982, as cited in Lyon et al., 2014). If the primary year is unknown, omit it rather than writing n.d.: Allport's diary (as cited in Nicholson, 2003). Only the secondary source appears in the reference list.

Does the original source go in my reference list?

In APA 7 and MLA 9, no; the list records only what you consulted. In Chicago 18 §14.160, yes: the original gets a bibliography or reference-list entry that ends with a Quoted in sentence naming the secondary source, and the secondary source also gets its own entry.

What is the MLA abbreviation for a secondary source?

MLA 9 §6.77 uses qtd. in, short for "quoted in," before the source you consulted: (qtd. in Damrosch 239). MLA uses the same abbreviation whether you are quoting or paraphrasing the original. The Style Center lets you put the original author's name in the prose, in the parenthetical, or in an endnote.

Which page number do I use?

In APA and MLA, the page in the work you read, because that is the page your reader can check — Damrosch 239, or a page of Nicholson you actually opened. In Chicago, the note gives the original's page as reported by the secondary source, then the secondary source's page: 269, quoted in …, 78. Never present a page you have not seen as if you had.

How does Chicago author-date handle a secondary source?

Cite the original in the text, for example (Zukofsky 1931, 269). In the reference list, the original's entry ends with "Quoted in Costello 1981, 78." and Costello gets a normal entry of its own. Do not import APA's as cited in phrase into the Chicago parenthetical.

When is it acceptable to cite a secondary source?

When the original is out of print, unavailable through any library you can reach, or written in a language you cannot read, and when an unpublished document such as Allport's diary is quoted in a published work. It is not acceptable simply because the textbook was closer to hand; a journal article with a DOI should be found and cited directly.

What if I find the original later?

Read the passage in context, cite the original directly, and add it to your list. Remove the secondary source unless you also cite it for claims of its own. Check that the summary you relied on was accurate; if the original says something different, revise your sentence, not just the citation.

Is this the same as a primary versus secondary source in history?

No. Historians call a diary primary and a monograph secondary because of how the document was produced. Citation manuals call Nicholson's book a secondary source because that is the copy you opened when you could not reach Allport's diary. Use primary versus secondary sources for the research-methods question.

How to Cite a Secondary Source in APA 7, MLA 9, and CMOS 18 [2026]

Quick Answer: How to Cite a Secondary Source

Name the original author, then point to the work you actually read. APA 7 puts as cited in inside the parenthetical or narrative citation and keeps the original out of the reference list. MLA 9 puts qtd. in before the source you consulted and keeps the original out of the works-cited list. Chicago 18 joins the two citations with quoted in and records both works. Never list a work you have not opened as if you had.

Official templates (APA 7 §8.6, MLA Style Center 20 September 2023, CMOS 18 §14.160)

APA 7 parenthetical, primary year known:

(Rabbitt, 1982, as cited in Lyon et al., 2014)

APA 7 narrative, primary year unknown:

Allport's diary (as cited in Nicholson, 2003)

APA 7 reference list:

Only Lyon et al. (2014) or Nicholson (2003). Rabbitt and Allport do not get entries.

MLA 9, original author in the sentence:

According to Alexander Pope, "A little learning is a dang'rous thing" (qtd. in Damrosch 239).

MLA 9 works cited:

Only Damrosch. Pope does not get an entry.

Chicago 18 first note:

1. Louis Zukofsky, "Sincerity and Objectification," Poetry 37 (February 1931): 269, quoted in Bonnie Costello, Marianne Moore: Imaginary Possessions (Harvard University Press, 1981), 78.

Chicago 18 author-date in-text (adapted from the official note):

(Zukofsky 1931, 269) — the Zukofsky reference entry ends with Quoted in Costello 1981, 78.

What "secondary source" means in a citation

In the citation manuals the phrase is about access, not about the kind of document. The primary source is the work whose idea, data, or words you are using. The secondary source is the work in which you encountered it. Nicholson's 2003 book quoting Allport's unpublished diary is the secondary source; the diary is the primary source. That is a different distinction from the historian's primary-versus-secondary split, where a diary is primary evidence and a monograph is secondary analysis. This guide uses the citation meaning throughout.

APA 7 §8.6 definition (Publication Manual, p. 258; Alamo Colleges reprint, 29 May 2026)

In scholarly work, a primary source reports original content; a secondary source refers to content first reported in another source.

The mechanic exists because the alternative is dishonest. If you cite Rabbitt (1982) directly after reading only Lyon and colleagues' summary, your reader assumes you checked Rabbitt, and any error in the summary becomes your error. If you cite only Lyon et al., you strip Rabbitt of credit for the idea. The as cited in chain is the only form that tells the truth about both.

Find the original first

Every manual leads with the same instruction. APA 7 §8.6 tells you to use secondary sources sparingly. MLA 9 §6.77 (Handbook p. 284) tells you to take material from the original whenever you can. CMOS 18 §14.160 calls the practice generally to be discouraged. Instructors read a page full of as cited in as a sign that you never left the textbook.

APA 7 §8.6, official wording

Cite secondary sources sparingly—for instance, when the original work is out of print, unavailable, or available only in a language that you do not understand.

If possible, as a matter of good scholarly practice, find the primary source, read it, and cite it directly rather than citing a secondary source.

CMOS 18 §14.160, official wording (live Q&A, opened 20 September 2026)

To cite a source from a secondary source ('quoted in . . .') is generally to be discouraged, since authors are expected to have examined the works they cite. If an original source is unavailable, however, both the original and the secondary source must be listed.

Copy the full reference of the original from the secondary source's reference list, note, or works-cited entry. That entry is why the secondary source cited it.
If the entry has a DOI, paste it into a browser or the DOI citation generator. A DOI resolves to the publisher's page; see how to use DOIs if it does not.
Search the title in your library catalogue and Google Scholar. Most twentieth-century journal articles are digitised, and many older public-domain books are free.
Request an interlibrary loan if the item is not in your collection. Turnaround is usually days, not weeks.
Once you have the original, read the passage in context and cite it directly. The chain disappears, and the secondary source stays in your list only if you also use it for something else.
If all of that fails, or the original is in a language you cannot read, cite it as a secondary source using the forms below.

When a secondary-source citation is defensible.
Situation	Cite the original directly?	Use the secondary form?
The original is a journal article with a DOI	Yes, always	No
The original is out of print and not in any library you can reach	Not possible	Yes
The original is in a language you do not read	Not without a translation	Yes, or cite a published translation directly — see reprints and translations
The original is an unpublished letter, diary, or interview quoted in a biography	Only if the archive is open to you	Yes — this is why APA's Allport diary example exists
You want to discuss how the secondary author interpreted the original	Cite both, each for its own words	Not needed; you are citing the secondary author's own claim
The secondary source is a lecture slide or study guide	Yes, find the source it summarises	Avoid

APA 7: "as cited in"

APA 7 §8.6 and the APA Style secondary sources page put the whole chain inside the in-text citation and keep the reference list honest: only works you consulted appear in it. The official examples below are the ones the Publication Manual prints on p. 258. The Alamo Colleges reprint (last updated 29 May 2026) matches that wording. APA does not publish a full reference-list entry for Lyon et al. (2014) in §8.6, so this page does not invent one.

APA 7 §8.6, official in-text rule

When citing a secondary source, provide a reference list entry for the secondary source that you used. In the text, identify the primary source and then write "as cited in" the secondary source that you used.

If the year of publication of the primary source is known, also include it in the text.

If the year of the primary source is unknown, omit it from the in-text citation.

APA 7 official in-text patterns

Parenthetical, primary year known:

(Rabbitt, 1982, as cited in Lyon et al., 2014)

Narrative, primary year unknown:

Allport's diary (as cited in Nicholson, 2003)

Reference list:

Lyon et al. (2014) and Nicholson (2003) are listed. Rabbitt (1982) and Allport are not.

Worked example: Allport's diary, read in Nicholson (2003)

Ian A. M. Nicholson's Inventing Personality: Gordon Allport and the Science of Selfhood (American Psychological Association, 2003) quotes Gordon Allport's unpublished diary. You could not obtain the diary. Every in-text form below points the reader to Nicholson, and Nicholson is the only entry the reference list gains. The book and DOI are real (10.1037/10514-000); the in-text pattern is APA's official Allport example.

APA 7, Nicholson 2003 as the secondary source you read

Reference list (the secondary source only):

Nicholson, I. A. M. (2003). Inventing personality: Gordon Allport and the science of selfhood. American Psychological Association. https://doi.org/10.1037/10514-000

Official narrative form:

Allport's diary (as cited in Nicholson, 2003)

Parenthetical paraphrase:

(Allport, as cited in Nicholson, 2003)

If you quote words Nicholson reprints, add the page of Nicholson you read (template):

Allport's diary (as cited in Nicholson, 2003, p. XX)

The page number belongs to Nicholson, because that is the page your reader can check. Do not copy a diary-page or archive-box number out of Nicholson's note into your parenthetical; you have not seen those pages. Use the APA in-text citation generator for the outer author–date pair and type the as cited in phrase by hand. Replace XX with the page of Nicholson you actually opened.

APA variations

Do not write n.d. for the original. If you do not know the primary year, omit it: (Allport, as cited in Nicholson, 2003). Writing n.d. would claim you checked Allport and found no date.
Ampersand versus and. Inside parentheses the secondary authors are joined with &; in a narrative sentence, with and. The rule is the same as for any APA citation; see how to cite multiple authors.
Three or more secondary authors. Shorten the secondary source with et al. exactly as you would normally: (Rabbitt, 1982, as cited in Lyon et al., 2014).
The primary source is a personal communication. A letter or diary quoted in a published work is still cited with as cited in, because your reader can find the published work. The personal communications rule applies only to communications you received.
Two different secondary sources report the same primary work. Cite each chain separately; do not merge them into one parenthetical.
You later obtain the original. Replace the chain with a direct citation and add the original to the reference list. Remove the secondary source unless you cite it for its own claims.

MLA 9: "qtd. in"

MLA 9 §6.77 (Handbook p. 284) handles indirect sources with the abbreviation qtd. in ("quoted in") placed before the source you consulted. MLA uses the same abbreviation whether you are quoting the original's words or paraphrasing them; the abbreviation signals that the material came to you through an intermediary. The works-cited list follows the same principle as APA: it contains only the work you read. The MLA Style Center page on citing indirect sources (published 20 September 2023) is the official home of the current worked examples.

MLA Style Center, official wording (20 September 2023)

When citing indirect sources, the name of the author of the original quotation can appear in the prose, in the in-text citation, or in an endnote.

The Style Center's example quotes Alexander Pope's line from An Essay on Criticism as it appears on page 239 of Leopold Damrosch Jr.'s The Imaginative World of Alexander Pope (University of California Press, 1987). Only Damrosch goes in the works-cited list. The three placements below are official; do not invent a Pope works-cited entry.

MLA Style Center official examples

Original author in the prose:

According to Alexander Pope, "A little learning is a dang'rous thing" (qtd. in Damrosch 239).

Original author in the parenthetical:

As a wise poet once wrote, "A little learning is a dang'rous thing" (Alexander Pope qtd. in Damrosch 239).

Original author in an endnote:

As a wise poet once wrote, "A little learning is a dang'rous thing." ¹

The endnote:

1. Alexander Pope qtd. in Damrosch 239.

Work cited (the secondary source only):

Damrosch, Leopold, Jr. The Imaginative World of Alexander Pope. U of California P, 1987.

Put the original author's name in your prose when you can, as the first Style Center option does. The parenthetical then only has to tell the reader where to look. There is no comma between the secondary author and the page number, because MLA never puts one before a page number; the MLA in-text guide covers that spacing. The Handbook's older classroom illustration uses Samuel Johnson through Boswell — Samuel Johnson admitted that Edmund Burke was an "extraordinary man" (qtd. in Boswell 289) — but editions of Boswell differ, so this page uses the Style Center's Damrosch line as the works-cited sample.

What MLA does not want

A works-cited entry for Pope or Johnson when you never opened Pope or Johnson. MLA's list is a record of what you consulted.
"Cited in" or "as cited in." Those are APA phrases; MLA's abbreviation is qtd. in, with a period after qtd.
Pope's original page or line number copied out of Damrosch. The page is Damrosch's, because that is where the reader will find the passage.
A bare (Damrosch 239) with no qtd. in after a sentence attributing the line to Pope. That reads as if Damrosch wrote the couplet.
qtd. in when you did read the original. If you are quoting Pope from Pope, cite Pope.

Chicago 18: "quoted in"

Chicago is the only one of the three that records both works in the note and the bibliography. CMOS 18 §14.160 (the same paragraph was §14.260 in CMOS 17) discourages the practice, then says that if the original is unavailable, both the original and the secondary source must be listed. The link word is quoted in, lowercase in a note and capitalised as Quoted in when it opens a new sentence in a bibliography entry. The live CMOS Q&A now cites §14.160 and prints the official note without a place of publication, which matches CMOS 18's rule that books published after 1900 no longer need a city.

Notes-Bibliography

The official sample cites Louis Zukofsky's February 1931 Poetry essay through Bonnie Costello's 1981 Harvard University Press book Marianne Moore: Imaginary Possessions. Both works are real. CMOS locates the quoted passage at page 269 of Poetry 37; the same issue also prints Zukofsky's longer essay "Sincerity and Objectification" beginning on page 272. Reproduce CMOS's official locator. Do not invent a different page to "correct" the sample.

CMOS 18 §14.160 official note (live Q&A)

First note:

1. Louis Zukofsky, "Sincerity and Objectification," Poetry 37 (February 1931): 269, quoted in Bonnie Costello, Marianne Moore: Imaginary Possessions (Harvard University Press, 1981), 78.

Chicago 18 notes-bibliography, completed from the official note

Shortened note (adapted from the official first note):

2. Zukofsky, "Sincerity and Objectification," 269, quoted in Costello, Marianne Moore, 78.

Bibliography (original, carrying the chain):

Zukofsky, Louis. "Sincerity and Objectification." Poetry 37 (February 1931): 269. Quoted in Bonnie Costello, Marianne Moore: Imaginary Possessions (Harvard University Press, 1981), 78.

Bibliography (secondary source, its own entry):

Costello, Bonnie. Marianne Moore: Imaginary Possessions. Harvard University Press, 1981.

Two details follow the official Zukofsky-and-Costello note. The original's page reference is the page where the quoted passage sits in the original, as reported by the secondary source, not the article's full page range. And the bibliography entry for the original ends with a full sentence beginning Quoted in, which is why the secondary source's details appear there in note form (first name first, parentheses around the publisher) rather than bibliography form. CMOS 18 no longer requires a place of publication for books published after 1900, so none appears above. Build the outer note with the Chicago footnote generator and add the quoted in clause by hand.

Author-Date

CMOS does not reprint a separate official author-date secondary-source sample. The chain moves into the reference list: the original gets an entry that ends with Quoted in plus the secondary source's author–date label and page, and the secondary source gets a normal entry of its own. The text citation then cites the original. The forms below adapt the official Zukofsky–Costello note to the Author-Date citation guide.

Chicago 18 author-date, adapted from the official §14.160 note

Reference list (original, carrying the chain):

Zukofsky, Louis. 1931. "Sincerity and Objectification." Poetry 37 (February): 269. Quoted in Costello 1981, 78.

Reference list (secondary source):

Costello, Bonnie. 1981. Marianne Moore: Imaginary Possessions. Harvard University Press.

In-text:

(Zukofsky 1931, 269)

If you want the chain visible in the sentence:

Zukofsky (1931, 269), as quoted by Costello (1981, 78), argued that …

Do not turn the author-date citation into (Zukofsky 1931, as cited in Costello 1981). That is APA's phrasing dropped into Chicago punctuation, and a Chicago reader will look for the Quoted in sentence in the list and not find it.

Three styles side by side

APA 7

Phrase:

as cited in

In the list:

Secondary source only

Primary year:

Include it if known; omit if not. Do not write n.d.

Page:

Secondary source's page, for quotations

MLA 9

Phrase:

qtd. in

In the list:

Secondary source only

Primary year:

Not part of the citation; mention it in prose if useful

Page:

Secondary source's page, no comma before it

Chicago 18

Phrase:

quoted in / Quoted in

In the list:

Both works

Primary year:

Part of the original's full citation

Page:

Original's page as reported, then the secondary source's page

Official samples, one row each: APA Rabbitt–Lyon, MLA Pope–Damrosch, Chicago Zukofsky–Costello.
Element	APA 7	MLA 9	Chicago 18 notes	Chicago 18 author-date
Text citation	(Rabbitt, 1982, as cited in Lyon et al., 2014)	Pope … (qtd. in Damrosch 239)	Note 1 with both works, joined by "quoted in"	(Zukofsky 1931, 269)
Entry for the original	None	None	Yes, ending "Quoted in …"	Yes, ending "Quoted in Costello 1981, 78."
Entry for the work you read	Yes — Lyon et al. or Nicholson	Yes — Damrosch	Yes — Costello	Yes — Costello
Connector capitalised?	No	No	Lowercase in notes, capital in the bibliography	Capital, starts a sentence
If the primary year is unknown	(Allport, as cited in Nicholson, 2003)	No change	Use n.d. in the original's citation	Use n.d. in the original's entry

A short checklist

Before you write as cited in, qtd. in, or quoted in

I searched for the original by DOI, title, and library catalogue, and I could not obtain it.
I named the original author in my sentence or parenthetical so the idea is credited correctly.
I used the connector for my style: as cited in (APA), qtd. in (MLA), quoted in (Chicago).
The page number in my APA or MLA citation is the page of the work I actually read.
APA or MLA: only the work I read is in my list. Chicago: both works are listed, and the original's entry carries the Quoted in sentence.
I did not write n.d. for the original in APA just because the secondary source omitted its year.
I will replace the chain with a direct citation if I obtain the original before submission.

Common mistakes

Listing the original in an APA or MLA list when you never read it. Both styles treat the list as a record of consultation.
Citing the original directly after reading only a summary. If the summary misreports it, the error is now yours, and a reader who checks will know.
Writing "cited in" or "quoted in" in APA. The APA phrase is as cited in.
Writing "as cited in" in MLA. The MLA abbreviation is qtd. in.
Giving the original's page numbers in APA or MLA. Give the page of the work you read.
Leaving out the secondary source's own entry in Chicago. Both works must be listed.
Using as cited in for a personal communication you received yourself. That is a personal communication citation, not a secondary one.
Filling a paper with chains because the textbook was convenient. Two or three are a judgement call; ten is a research problem.

Generate the outer citation, then add the chain

Cite the work you read as a normal book, article, or web page. The generator produces the reference entry and the author–date or author–page pair; you add as cited in, qtd. in, or quoted in and the original author's name by hand, because no generator can verify a source you have not opened.

In-text citation generator →Chicago footnote generator →DOI citation generator →

Frequently asked questions

What is a secondary source in a citation?: It is the work in which you read about another work. The original work is the primary source; the one you actually opened is the secondary source. APA 7 §8.6 defines a secondary source as content first reported in another source. That is a question of access, not of document type, and it is not the historian's primary-versus-secondary test.
How do I write "as cited in" in APA 7?: Name the primary author and year, then the phrase as cited in, then the secondary source in normal author–date form: (Rabbitt, 1982, as cited in Lyon et al., 2014). If the primary year is unknown, omit it rather than writing n.d.: Allport's diary (as cited in Nicholson, 2003). Only the secondary source appears in the reference list.
Does the original source go in my reference list?: In APA 7 and MLA 9, no; the list records only what you consulted. In Chicago 18 §14.160, yes: the original gets a bibliography or reference-list entry that ends with a Quoted in sentence naming the secondary source, and the secondary source also gets its own entry.
What is the MLA abbreviation for a secondary source?: MLA 9 §6.77 uses qtd. in, short for "quoted in," before the source you consulted: (qtd. in Damrosch 239). MLA uses the same abbreviation whether you are quoting or paraphrasing the original. The Style Center lets you put the original author's name in the prose, in the parenthetical, or in an endnote.
Which page number do I use?: In APA and MLA, the page in the work you read, because that is the page your reader can check — Damrosch 239, or a page of Nicholson you actually opened. In Chicago, the note gives the original's page as reported by the secondary source, then the secondary source's page: 269, quoted in …, 78. Never present a page you have not seen as if you had.
How does Chicago author-date handle a secondary source?: Cite the original in the text, for example (Zukofsky 1931, 269). In the reference list, the original's entry ends with "Quoted in Costello 1981, 78." and Costello gets a normal entry of its own. Do not import APA's as cited in phrase into the Chicago parenthetical.
When is it acceptable to cite a secondary source?: When the original is out of print, unavailable through any library you can reach, or written in a language you cannot read, and when an unpublished document such as Allport's diary is quoted in a published work. It is not acceptable simply because the textbook was closer to hand; a journal article with a DOI should be found and cited directly.
What if I find the original later?: Read the passage in context, cite the original directly, and add it to your list. Remove the secondary source unless you also cite it for claims of its own. Check that the summary you relied on was accurate; if the original says something different, revise your sentence, not just the citation.
Is this the same as a primary versus secondary source in history?: No. Historians call a diary primary and a monograph secondary because of how the document was produced. Citation manuals call Nicholson's book a secondary source because that is the copy you opened when you could not reach Allport's diary. Use primary versus secondary sources for the research-methods question.

Quick Answer: How to Cite a Secondary Source

What "secondary source" means in a citation

Find the original first

APA 7: "as cited in"

Worked example: Allport's diary, read in Nicholson (2003)

APA variations

MLA 9: "qtd. in"

What MLA does not want

Chicago 18: "quoted in"

Notes-Bibliography

Author-Date

Three styles side by side

A short checklist

Common mistakes

Generate the outer citation, then add the chain

Frequently asked questions

Related guides and official manuals