Reference Universe

Britannica Academic Edition
Updated daily. The combination of the Encyclopædia Britannica and Merriam-Webster’s Collegiate Dictionary and Thesaurus, magazines and periodicals, and many other research tools provides a variety of reliable sources.
Encyclopedia of Environmental Issues - 2011
Provides information from numerous fields of knowledge relevant to the study of environmental issues, including biology, geology, anthropology, demographics, genetics, and engineering, and explains the interrelationships of these issues.