What to do when using an eBook as a reference?
(From the Chicago style manual:)
Book published electronically
"If a book is available in more than one format, cite the version you consulted. For books consulted online, list a URL; include an access date only if one is required by your publisher or discipline. If no fixed page numbers are available, you can include a section title or a chapter or other number."
Austen, Jane. Pride and Prejudice. New York: Penguin Classics, 2007. Kindle edition.
Kurland, Philip B., and Ralph Lerner, eds. The Founders’ Constitution. Chicago: University of Chicago Press, 1987. Accessed February 28, 2010. http://press-pubs.uchicago.edu/founders/.
For an article on this topic:
