A manual for writers of research papers, theses, and dissertations, 7th edition - Kate L. Turabian 2007

Online and other electronic books
Parenthetical citations–reference list style: citing specific types of sources
Part II. Source Citation

For online books, follow the guidelines for print books. In addition to the usual elements, include the URL and the date you accessed the material in your reference list (see 15.4.1, 19.1.8). Note that a URL alone is not sufficient; you must provide the full facts of publication, as far as they can be determined, so that a reader can search for the source even if the URL changes. If page numbers are not available, you may identify the location of a cited passage in a parenthetical citation by adding a descriptive locator (such as a preceding subheading) following the word under.

R: Samora, Julian, and Patricia Vandel Simon. 2000. A history of the Mexican-American people. Rev. ed. East Lansing, MI: Julian Samora Research Institute, Michigan State University. http://www.jsri.msu.edu/museum/pubs/MexAmHist/chapter14.html#six (accessed December 19, 2005).

P: (Samora and Vandel Simon 2000, under “Civil War in Mexico”)

or

(Samora and Vandel Simon 2000)

When you cite books published in other electronic formats, such as those available for download or other delivery from a bookseller or library, identify the format (CD-ROM, Microsoft Reader e-book).

R: Davenport, Thomas H., and John C. Beck. 2001. The attention economy: Understanding the new currency of business. Cambridge, MA: Harvard Business School Press. TK3 Reader e-book.

Hellman, Hal. 2004. Great feuds in technology: Ten of the liveliest disputes ever. New York: John Wiley. Rocket e-book.