Modern Angelology
Lives of the Saints by Alban Butler.
Lives of the Saints by Sabine Baring-Gould.
The Liturgical Year by Dom Guéranger.
Our Birthday Bouquet Culled from the Shrines of the Saints and the Gardens of the Poets by Eleanor C. Donnelly.
The Lives of Saints, with Other Feasts of the Year, According to the Roman Calendar by Peter Ribadeneira.
Medieval Angelology
The Cult of Saints in Late Antiquity Database (translation and summary)
About the originating account, Liber de apparitione Sancti Michaelis.
Breviarium Romanum – Latin & English.
Art & Architecture
Index of Medieval Art – Appearing at Castel Sant’Angelo & Apparation at Monte Gargano
Catalogo generale dei beni culturali
Warburg Institute Iconographic Database
A Guide to Christian Iconography: Images, Symbols, and Texts
The sanctuary of Monte Sant’Angelo
Music
Nihil sub sole novum 