Walsh, Michael J. (2003). The Conclave: A Sometimes Secret and Occasionally Bloody History of Papal Elections. Lanham, Maryland: Sheed & Ward. p. 81. ISBN978-1-58051-135-3.
Bagliani 1972, p. ? Bagliani, Agostino Pallavicini (1972). Cardinali di curia e familiae cardinalizie dal 1227 al 1254. Italia Sacra vols 18–19. Padua, Italy: Antenore. OCLC2205084. A standard account.