A secondary source is one where the author of the work you are reading (e.g. book, article, etc.) is referencing or quoting another author's work.
Use secondary sources sparingly; you should always try to locate the original source of information which is cited in a work that you have read. This is not, however, always possible: sometimes the original work is out of print, unavailable through your usual sources or not available in English.
If you read an article or book which cites or quotes some information that you want to use, always refer to both the original source and the source where you found the information. The words Cited in or Quoted in are used the indicate how the information from the original source was been used in the article that you have read.
Citing:
If you read an article by Alex Reid, in which he cites information from a previous study by Seidenberg and McClelland, and you wish to refer to this information in your assignment:
• You would acknowledge Seidenberg and McClelland in the text:
Seidenberg and McClelland’s 1989 study, published in volume 96 of the Psychological Review, (cited in Reid 2007) found that the paranormal…
• In your reference list at the end of your assignment, cite the secondary source because that is where you obtained the information:
Reid, A. S. 2007. "Study of Multiple Paranormal Phenomena." Journal of Abnormal Psychology 45, no. 1 (February): 13-26.
Quoting:
If you wish to use a quote by Zukofskyin, reproduced in an article by Costello, in your assignment:
• You would acknowledge Zukofskyin in the text:
In Louis Zukofskyin's "Sincerity and Objectification," from the February issue of Poetry magazine (quoted in Costello 1981)...
• In your reference list at the end of your assignment, cite the secondary source where you located the quote:
Costello, Bonnie. 1981. Marianne Moore: Imaginary Possessions. Cambridge, MA: Harvard University Press.