Gaya APA

Enger, E, D., Smith, B, F. (1997). Environmental science: A study of interrelationships 6th edition (6th Edition). Boston: McGraw-Hill Book.

Gaya MLA

Enger, Eldon, D.., Smith, Bradley, F.. "Environmental science: A study of interrelationships 6th edition". 6th Edition Boston: McGraw-Hill Book, 1997. Printed Book.