APA

Billington R. A., . (1960). Westward expansion: a history of the American frontier. New York: Macmillan.

Chicago

Billington Ray Allen, . 1960. Westward expansion: a history of the American frontier. New York: Macmillan.

Harvard

Billington R. A., . (1960). Westward expansion: a history of the American frontier. New York: Macmillan.

MLA

Billington Ray Allen, . Westward expansion: a history of the American frontier. New York: Macmillan. 1960.