Citing a citation, also known as citing an indirect source, is when a writer cites information that is quoted from a different source. Although all of the major citation systems encourage writers to track down the original source of the information and to use it as the source in the new paper, the citation systems recognize that this is sometimes impossible. In that case, it is okay to cite indirect sources as long as proper credit is given to both the original source and the intermediary source in which the the quotation was found.
Determine the citation system in use in the paper. Although they use similar formats for dealing with indirect citations, MLA, APA, and Chicago styles all differ in their approach to the way to format this kind of reference.
Find the full citation for the original work that this citation is coming from. It should be available in the Bibliography or Works Cited page of the quoting document.
Include the appropriate addition to the in-text citation to show that you are citing an indirect source. This differs based on the citation system. Although MLA discourages indirect sources, if used, the parenthetical citation should use "qtd. in" before the typical MLA citation. For APA format, add "as cited in" before the typical in-text citation of author, year, and page number. The Chicago system of citation calls for the original source of the quotation to be cited when the citation is used.
Add a citation for both the work that the citation is coming from and the source of the original text in both APA and MLA formats. For the original source, add "Quoted in (author's name of the citing work)" to the end of the citation to show where the information came from. In Chicago style, the original source is cited and then followed by "Quoted In" and then immediately followed by the citation for the work in which the citation was found. In Chicago, the citations for both works are considered one citation and go on one line.