
Gale Virtual Reference Library
Principally dealing with history, wildlife and science. Many of the titles are provided by the publisher Dorling Kindersley and as such are fully illustrated and specifically written for younger readers aged 6-14. Also includes Grzimek's Animal Life Encyclopedia and International Dictionary of Films and Filmmakers.

Oxford English Dictionary
The full 23 Volumes of the internet's biggest, most prestige-laden reference book.

Oxford Dictionaries Pro
Offers quick search access to definitions of words, phrases, and idioms, with expert guidance on style and usage, grammar, etc.