II: The Popes During the Carolingian Empire, 795–858" (1906)* 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==*Vita Operaque by Migne Patrologia Latina with analytical indexes
II: The Popes During the Carolingian Empire, 795—858 (1906)* 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)