How to Cite from a Digital Source
This is an example of how you would cite Romeo and Juliet if you used the iBooks version of the play.
Shakespeare, William. The Tragedy of Romeo and Juliet. 1595. Digital file.
If you have the traditional bibliographic information (author, title, publisher, publishing city, and publication date), use the regular format for a bibliographic entry. Replace the word “Print” at the end with the type of file name or the words Digital file. If you do not have all the information, use the author, title, date, and medium (as in the example above).