TY  - BOOK
AU  - Whalen, Brett Edward
TI  - The Two Powers: The Papacy, the Empire, and the Struggle for Sovereignty in the Thirteenth Century
SN  - 9780812296129
PB  - Walter de Gruyter
KW  - History
UR  - http://www.degruyter.com/isbn/9780812296129
ER  -