Gaya APA

Billington, R, A. (1974). Westward expansion : a history of the American frontier (4th. ed). New York: Macmillan Pub. Co., Inc..

Gaya MLA

Billington, Ray, Allen. "Westward expansion : a history of the American frontier". 4th. ed New York: Macmillan Pub. Co., Inc., 1974. Text.