Frederick Barbarossa's conflict with the papacy : a problem of church and state / by Paul J. Knapke, c.pp.s. - Knapke, Paul J. (OLS)http://pul/name/106737; Catholic University of America. Tesi. (OLS)http://pul/name/106692 (The Catholic University of America, 1939)
Sul front.: no. 55.
Tesi. Universitas Catholica Americae, Washingtonii. S. Facultas Theologica. 1939.
Bibliografia in nota a piè pagina.