Gaya APA

Enger, E, D., Smith, B, F. (2004). Environmental science: a study of interrelationships. 9th ed. . Boston, Massachusetts: McGraw-Hill.

Gaya MLA

Enger, Eldon, D.., Smith, Bradley, F.. "Environmental science: a study of interrelationships. 9th ed.". Boston, Massachusetts: McGraw-Hill, 2004. Text.