Botkin, D. B., & Keller, E. A. (2003). Environmental science: Earth as a living planet (4th ed.). Wiley.

Botkin, Daniel B., and Edward A. Keller. Environmental Science: Earth as a Living Planet. 4th ed. New York: Wiley, 2003.

Botkin, Daniel B., and Edward A. Keller. Environmental Science: Earth as a Living Planet. 4th ed. Wiley, 2003.