Gaya APA

Swanson, C, P., E, I, G, R. (1982). Essentials of physical geography . Philadelphia: Philadelphia: Saunders College; 1982.

Gaya MLA

Swanson, Carl, P.., E, I., Gabler,, Robert. "Essentials of physical geography". Philadelphia: Philadelphia: Saunders College; 1982, 1982. Text.