Botkin, D. B., & Keller, E. A. (2007). Environmental science: Earth as a living planet (6th ed.). Wiley.

Botkin, Daniel B., and Edward A. Keller. Environmental Science: Earth as a Living Planet. 6th ed. Hoboken, NJ ; New Delhi: Wiley, 2007.

Botkin, Daniel B., and Edward A. Keller. Environmental Science: Earth as a Living Planet. 6th ed. Wiley, 2007.