When I’m doing heavy research, I use JSTOR, Library of Congress, and the Biblioteque Nationale de France (BNF). The BNF is a great resource. If you haven’t been to the library’s site, go visit.
Imagine my surprise (and great delight!) to discover that they have an electronic copy of Salomon Reinach’s Epona, La Deesse Gauloise des Chevaux. Not only is the whole book available online, you can embed a copy of if on your web site.