Cita APA (7a ed.)

Whalen, B. E. (2019). The Two Powers: The Papacy, the Empire, and the Struggle for Sovereignty in the Thirteenth Century. University of Pennsylvania Press.

Cita Chicago Style (17a ed.)

Whalen, Brett Edward. The Two Powers: The Papacy, the Empire, and the Struggle for Sovereignty in the Thirteenth Century. Philadelphia: University of Pennsylvania Press, 2019.

Cita MLA (8a ed.)

Whalen, Brett Edward. The Two Powers: The Papacy, the Empire, and the Struggle for Sovereignty in the Thirteenth Century. University of Pennsylvania Press, 2019.