Modern Angelology
Lives of the Saints by Sabine Baring-Gould.
Our Birthday Bouquet Culled from the Shrines of the Saints and the Gardens of the Poets by Eleanor C. Donnelly.
“Saint Gabriel” by Frederick William Faber. (also here)
Biblical texts
Medieval Hagiography
The Cult of Saints in Late Antiquity Database
Breviarium Romanum – Latin.
Art & Architecture
Catalogo generale dei beni culturali
POP : la plateforme ouverte du patrimoine
Warburg Institute Iconographic Database (see also The Annunciation, Gabriel Explaining Daniel’s Vision, Angel Appearing to Daniel)
A Guide to Christian Iconography: Images, Symbols, and Texts
Sacred and Legendary Art volume I by Mrs. Jameson.
A Handbook of Christian Symbols and Stories of the Saints as Illustrated in Art by Clara Erskine Clement.
A Garner of Saints: Being a Collection of the Legends and Emblems Usually Represented in Art by Allen Hinds.
The Saints in Art with Their Attributes and Symbols, Alphabetically Arranged by Margaret E. Tabor.
Saints and their Symbols: A Companion in the Churches and Picture Galleries of Europe by E. A. Greene.
Emblems of Saints by Which They Are Distinguished in Works of Art by F. C. Husenbeth.
Sacred Symbols in Art by Elizabeth Edwards Goldsmith.
Music
Cantus: A Database for Latin Ecclesiastical Chant
Hymns to Saint Gabriel in the Parochial Hymn Book
Customs & Devotions
Heortology: A History Of The Christian Festivals From Their Origin To The Present Day by Heinrich Kellner.
Nihil sub sole novum 