A secondary source is a source that quotes or paraphrases another source. An example would be Sontag's On Photography cited in Zelizer's book Remembering to Forget. Secondary sources should be used sparingly. Try to locate the original source of information cited in the a work if it is possible.
In your footnote, cite the original source, as well as the source where you located in the information. In your bibliography, cite only the source that you consulted.
Bibliography:
Lienhard, Joseph T., editor. Exodus, Leviticus, Numbers, Deuteronomy. Ancient Christian Commentary. Downers Grove, IL: InterVarsity Press, 2001.
Footnote:
1. Augustine, “Tractate on the Gospel of John 20.2,” in Fathers of the Church: A New Translation (Washington, DC: Catholic University of America Press, 1947), 79:164, quoted in Joseph T. Lienhard, ed., Exodus, Leviticus, Numbers, Deuteronomy, Ancient Christian Commentary (Downers Grove, IL: InterVarsity Press, 2001), 104.
Reference List:
Give the citation for your secondary source. Use the appropriate citation format for your source, e.g. book or article.
Example:
Zelizer, Barbie. 2003. Remembering to Forget: Holocaust Memory through the Camera's Eye. Chicago: University of Chicago Press.
In-Text Citation:
In Susan Sontag's 1977 book On Photography (quoted in Zelizer 2003, 11)...
Note: Cite the original source in the running text of your paper. Cite the secondary source in parenthesis with "quoted in."