APA (7th ed.) Citation

Commager, H. S. (1964). The twentieth century American. Westermann.

Chicago Style (17th ed.) Citation

Commager, Henry Steele. The Twentieth Century American. Braunschweig ; München [u.a.]: Westermann, 1964.

MLA (9th ed.) Citation

Commager, Henry Steele. The Twentieth Century American. Westermann, 1964.