Gaya APA

Enger, E, D., Smith, B, F. (2004). Environmental Science : A Study of Interrelationships (Ed. 9). Boston: Mcgraw Hill, Inc.

Gaya MLA

Enger, Eldon, D.., Smith, Bradley, F.. "Environmental Science : A Study of Interrelationships". Ed. 9 Boston: Mcgraw Hill, Inc, 2004. Text.