MLA Handbook by 
Cite Right
Doing Honest Work in College
Create citations in MLA, APA, or Chicago/Turabian formats for a wide variety of material types.
Try to avoid quoting works "cited in" other works ~ BUT ~ sometimes you may have to use an indirect source. An indirect source is a source cited in another source. For such indirect quotations, use "qtd. in" to indicate the source you actually consulted. For example:
As Carter Martin states, "Only a few characters are more deeply evil, and they incarnate the force and living presence of a chaotic, destructive, and dark principle of evil in the world; these characters are agents of or physical embodiments of the devil" (qtd. in Shaw 474).
Refers to this in Works Cited:
Shaw, Mary Neff. "Responses to God's Grace: Varying Degrees of
Doubt in Flannery O'Connor's Character Types." CLA Journal 44.4
(June 2001): 471-479. Rpt. in Short Story Criticism. Ed. Janet
Witalec. Vol. 61. Detroit: Gale, 2003. Literature Resource Center.
Web. 1 Dec. 2010.
Online tutorials to help you understand why you need to cite: