Gaya APA

, ., E., I, G, R. (1982). Essentials of physical geography . Philadelpia: Philadelpia: Saunders College Publishing; 1982.

Gaya MLA

, ., E., I., Gabler,, Robert. "Essentials of physical geography". Philadelpia: Philadelpia: Saunders College Publishing; 1982, 1982. Text.