Internet Archive

Internet Archive (or archive.org to use the short form of its web address as a name), in it's words, "is a non-profit library of millions of free books, movies, software, music, and more." A search for public domain works will produce links to copies of those works either at the Internet Archive itself or at other sites, usually libraries or sites like Project Gutenberg. Usually they come in various formats, PDF, of course, is most common. But there is usually a copy you can read directly on the web and formatted as if you are reading an open book and turning the pages. If you have DjVu reader, you can also download that format and read it in same as straight off the web.

Since the actual history and the stories and myths of the canonical period of Mythic Europe, and of any setting but the most modern or entirely originally fictitious setting, have been the subjects of written works that are more than a century old, they often can be found free through the Internet archive. In fact, in many of the Fifth Edition titles that included bibliographies, there is at least one listed work that is in the public domain, and thus likely to be found at through the Internet Archive.