Whalen, B. E. (2019). The Two Powers: The Papacy, the Empire, and the Struggle for Sovereignty in the Thirteenth Century. University of Pennsylvania Press.
Chicago Style (17th ed.) CitationWhalen, Brett Edward. The Two Powers: The Papacy, the Empire, and the Struggle for Sovereignty in the Thirteenth Century. Philadelphia: University of Pennsylvania Press, 2019.
MLA (8th ed.) CitationWhalen, Brett Edward. The Two Powers: The Papacy, the Empire, and the Struggle for Sovereignty in the Thirteenth Century. University of Pennsylvania Press, 2019.
Warning: These citations may not always be 100% accurate.