title_body: How can I put footnotes in an ebook?
upvoted_answer: I don't think there is an official way to put footnotes, at least in EPUB2. What I do in the ebooks I prepare is to add an hyperlink to the note (placed in a chapter of its own at the end of the book, and to put at the end of the note another hyperlink which goes back to the original position. It's a bit ugly, but at least it helps readers (in the sense of people, not devices!)