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The Pope Encyclopedia: An A to Z of the Holy See, Matthew Bunson, Crown Trade Paperbacks, New York, 1995.
The Papacy, Bernhard Schimmelpfennig, Columbia University Press, New York, 1984.
Lives of the Popes, Richard P. McBrien, Harper Collins, San Francisco, 1997.
Papal Genealogy, George L. Williams, McFarland& Co., Jefferson, North Carolina, 1998.
Sex Lives of the Popes, Nigel Cawthorne, Prion, London, 1996.
Popes and Anti-Popes, John Wilcock, Xlibris Corporation, 2005.
La véritable histoire des papes, Jean Mathieu-Rosay, Grancher, Paris, 1991.