GE10.E53 Eblen, Ruth A and Walter R Eblen, eds. The Encyclopedia of the Environment. Houghton Miflin Company, 1994. One volume, with entries ranging from a few paragraphs to a few pages, on people, organizations, broad topics, and focused issues.
Some entries have suggestions for further reading.
Ref BL31.E46 Eliade, Mircea. The Encyclopedia of Religion. The best of the religion encyclopedias. Lengthy articles written by scholars. Each article ends with citations to additional sources.