Citation, Documentation of Sources

Q. I would like to quote a sentence from my textbook that was initially a quote from another source. Which source do I cite? Do I cite my textbook or the original source (or both)?

A. Please see CMOS 14.260: “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.” Here’s an example:

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