Cunningham, W. P., & Saigo, B. W. (2001). Environmental science: A global concern (6th ed.). McGraw-Hill.

Cunningham, William P., and Barbara Woodworth Saigo. Environmental Science: A Global Concern. 6th ed. Boston: McGraw-Hill, 2001.

Cunningham, William P., and Barbara Woodworth Saigo. Environmental Science: A Global Concern. 6th ed. McGraw-Hill, 2001.