APA (7th ed.) Citation

Ullmann, W. (1965). A history of political thought: The Middle Ages. Penguin Books.

Chicago Style (17th ed.) Citation

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

MLA (8th ed.) Citation

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