Kirsch, Johann Peter. "Pope John XI." The Catholic Encyclopedia. Vol. 8. New York: Robert Appleton Company, 1910. http://www.newadvent.org/cathen/08426a.htm. Accessed 22 Aug 2014.
Date of birth unknown, became pope in 931; d. 936. He was the son of Marozia by her first marriage withAlberic; some, taking Liutprand and the "Liber Pontificalis" as their authority, assert that he was the naturalson of Sergius III ("Johannes, natione Romanus ex patre Sergio papa", "Liber Pont." ed. Duchesne, II, 243). Through the intrigues of his mother, who ruled at that time in Rome, he was raised to the Chair of Peter, and was completely under the influence of the Senatrix et Patricia of Rome. To strengthen her own power Marozia married her brother-in-law Hugh, King of Provence and Italy, whose reign in Rome was so tyrannical that a strong opposition party sprang up among the nobles under the leadership of Alberic II, the younger son of Marozia. This party succeeded in overthrowing the rule of Marozia and Hugh; Marozia was cast into prison, but her husband escaped from the city. In this way Alberic became ruler of Rome, and the pope, who suffered by his mother's fall, now became almost entirely subject to his brother, being only free in the exercise of his purely spiritual duties. All other jurisdiction was exercised through Alberic. This was not only the case insecular, but also in ecclesiastical affairs. It was at the instance of Alberic that the pallium was given to Theophylactus, Patriarch of Constantinople (935), and also to Artold, Archbishop of Reims (933). It was this pope who sat in the Chair of Peter during its deepest humiliation, but it was also he who granted many privileges to the Congregation of Cluny, which was later on so powerful an agent of Church reform.
Liber Pontificalis, ed. DUCHESNE, II, 243; JAFFÉ, Regesta (2nd ed.), I, 454 sq.; LANGEN, Gesch. der röm. Kirche, II, 329-31; REUMONT,Gesch. der Stadt Rom, II, 231 sqq.