Cita APA (7th ed.)

Gilbert, M. (1997). A history of the twentieth century. Avon Books.

Cita Chicago (17th ed.)

Gilbert, Martin. A History of the Twentieth Century. New York: Avon Books, 1997.

Cita MLA (9th ed.)

Gilbert, Martin. A History of the Twentieth Century. Avon Books, 1997.