[d] Victor Duruy, Histoire du Moyen Age.
[e] O. J. Reichel, The See of Rome in the Middle Ages.
[f] J. Bass Mullinger, article on “Popedom,” in the Encyclopædia Britannica.
[g] Henry Stebbing, History of the Christian Church.
[h] John Wm. Draper, History of the Intellectual Development of Europe.
[i] Gregory of Tours, Annales Francorum.
[j] Andreas Thiel, Epistolæ Romanorum Pontificorum.
[k] Gregory the Great, Letters and Dialogues.
[l] Edward Gibbon, Decline and Fall of the Roman Empire.