General reference works are good places to check facts and get basic information. Although general encyclopedias are often a good place to find background about your topic, you should rarely use them in your final paper. Most instructors expect you to rely on more specialized sources.
Here are a few frequently used general references:
American National Biography
National Geographic Atlas of the World
The New Encyclopaedia Britannica
The Oxford English Dictionary
Statistical Abstract of the United States http://www.census.gov/compendia/statab
Wikipedia http://wikipedia.org/
World Almanac and Book of Facts