Hence John too was probably the son of Marozia and Alberic I.
Theodora was characterized by the aforementioned Liutprand as a "shameless whore.. exercised power on the Roman citizenry like a man". Liutprand, a bishop of Cremona, was described by the Catholic Encyclopedia as frequently being unfair to adversaries and could be partial in his judgments.
E. Dümmler, Auxilius u. Vulgarius. Quellen und Forschungen zur Geschichte des Papsttums im Anfange des zehnten Jahrhunderts, Leipzig 1866, pp. 12–26
P. Fedele, Ricerche per la storia di Roma e del papato al secolo X, in "Archivio della Società Romana di Storia Patria", 33, 1910, pp.
177–247
34, 1911, pp. 75–115 e 393–423
L. Duchesne, Serge III. et Jean XI., in "Mélanges d'archéologie et d'histoire", 33 (1913), pp. 25–64Ferdinand Gregorovius, Storia di Roma nel medioevo, New Compton Editori Srl, Roma 1972Lexikon des Mittelalters, München 2002Daniela Schumacher-Immel (1996).
"Theodora, die Ältere". In Bautz, Traugott. Biographisch-Bibliographisches Kirchenlexikon (BBKL) (in German) 11. Herzberg: Bautz. cols.
919–920. .
