Subject encyclopedias have a wealth of background information that can provide you with a strong foundation upon which to build your research.
Example: To find a geography encyclopedia, do a SOUTHcat keyword search for encyclop? geograph?
Concise Encyclopedia of Economics
Dictionary of Human Geography
Europa World Year Book
Geo-Data: The World Geographical Encyclopedia
Globalization : Encyclopedia of Trade, Labor, and Politics
Worldmark Encyclopedia of the Nations