Валентин (папа римский): различия между версиями

* Mann, Horace K., The Lives of the Popes in the Early Middle Ages, Vol. 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).