Gaya APA

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

Gaya MLA

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