Three encyclopedias at different reading levels: Elementary, Middle, and High School. Articles include videos and weblinks.

World Book

Grolier

Reference source with information about countries, states, and provinces. Each geographic place has a traditional article, plus photos, videos and interviews. Articles are divided between Kids Edition and World Edition.

The largest and most popular encyclopedia in the world. Articles are written by multiple authors whose names are not disclosed, and their expertise not known. Because of this, it is not considered authoritative or acceptable for school projects. Reading level is not controlled.