Quellen: Aus katholischer Sicht: Robert F. Kardinal Bellarmin, Power of the Popes in Temporal Affairs, Washington; Henry Edward Kardinal Manning, The Temporal Power of the Vicar of Jesus Christ, London, 1862; James Kardinal Gibbons, Der Glaube unserer Väter, Kapitel 5, 9, 10 und 12. GK 715.1
Aus protestantischer Sicht: Trevor Gervase Jalland, The Church and the Papacy, London, 1944; R.F. Littledale, Petrine Claims, London, 1899; James T. Shotwell/ Louise R. Soomis, The See of Peter, New York, 1927; Christopher B. Coleman, The Treatise of Lorenzo Valla on the Donation of Constantine, New York, 1914. GK 715.2