Cita APA (7a ed.)

Unger, I., & Unger, D. (1990). Twentieth century America. St. Martin's Pr.

Cita Chicago Style (17a ed.)

Unger, Irwin, y Debi Unger. Twentieth Century America. New York, NY: St. Martin's Pr, 1990.

Cita MLA (9a ed.)

Unger, Irwin, y Debi Unger. Twentieth Century America. St. Martin's Pr, 1990.