APA (7th ed.) Citation

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

Chicago Style (17th ed.) Citation

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

MLA (9th ed.) Citation

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