IV: The Popes in the Days of Feudal Anarchy, 891-999" (1910)* DeCormenin, Louis Marie; Gihon, James L., "A Complete History of the Popes of Rome, from Saint Peter, the First Bishop to Pius the Ninth" (1857)==Notes====External links==* Opera Omnia by Migne Patrologia Latina with analytical indexes* Crescenzi family
IV: The Popes in the Days of Feudal Anarchy, 891-999 (1910)*DeCormenin, Louis Marie; Gihon, James L., A Complete History of the Popes of Rome, from Saint Peter, the First Bishop to Pius the Ninth (1857)