Gaya APA

Enger, E, D., Smith, B, F. (2013). Environmental Science: A Study of Interrelationships thirteenth edition (Thirteenth Edition). USA: The MC Graw Hill Companies.

Gaya MLA

Enger, Eldon, D.., Smith, Bradley, F.. "Environmental Science: A Study of Interrelationships thirteenth edition". Thirteenth Edition USA: The MC Graw Hill Companies, 2013. Text.