Modern Hagiography
Lives of the Saints by Alban Butler.
Lives of the Saints by Sabine Baring-Gould.
Medieval Hagiography
The Cult of Saints in Late Antiquity Database
Writings of Pope Julius
His correspondence (not in the public domain)
Art & Architecture
Panel showing consecration of Saint Donatus, lower register, second from left) – Betto di Francesco – Giovanni di Francesco (1364-1375), Arca di San Donato