APA (7th ed.) Citation

Erdmann, C. (1977). The origin of the idea of crusade. Princeton University Press.

Chicago Style (17th ed.) Citation

Erdmann, Carl. The Origin of the Idea of Crusade. Princeton, N.J: Princeton University Press, 1977.

MLA (9th ed.) Citation

Erdmann, Carl. The Origin of the Idea of Crusade. Princeton University Press, 1977.