What Every American Needs to Know Ref. 1988 Dictionary of the Environment Ref. McGraw-Hill Dictionary of Chemistry Ref. 1984 Presidential-Congressional Political Dictionary Ref. Webster's New Geographical Dictionary R Ref.
General encyclopedias are useful for broad background information and to identify facts.
Britannica Online Encyclopedia Americana Ref. Encyclopedia Americana Annual Ref. New Encyclopaedia Britannica Ref. World Book Ref. Subject specific encyclopedias are useful for background information on a topic.