APA

Ullmann W., . (1970). A history of political thought: the middle ages. Harmondsworth: Penguin Books.

Chicago

Ullmann Walter, . 1970. A history of political thought: the middle ages. Harmondsworth: Penguin Books.

Harvard

Ullmann W., . (1970). A history of political thought: the middle ages. Harmondsworth: Penguin Books.

MLA

Ullmann Walter, . A history of political thought: the middle ages. Harmondsworth: Penguin Books. 1970.