APA-referens (7:e uppl.)

Ullmann, W. (1965). A history of political thought: The middle ages. Penguin.

Chicago-referens (17:e uppl.)

Ullmann, Walter. A History of Political Thought: The Middle Ages. Harmondsworth: Penguin, 1965.

MLA-referens (9:e uppl.)

Ullmann, Walter. A History of Political Thought: The Middle Ages. Penguin, 1965.