Ref d o c.fr "Over 53 million records of articles, books, reports and conference proceedings in the fields of Science, Technology, Medicine, Humanities and Social Sciences, from 1823 up to the present day (with daily updates)" link
Using the Google Adwords keyword tool, I discovered that “ebooks” has 13.6 million global monthly searches and “e-books” has 4.1 million, meaning that roughly triple the amount of people search for “ebooks” versus “e-books.” An interesting post by Greenfield link