Modern Hagiography
Bibliotheca Sanctorum (both)
Martyrologium Romanum (both)
Roman Martyrology (Vienne)
Lives of the Saints by Alban Butler. (Vienne)
Lives of the Saints by Sabine Baring-Gould. (Vienne)
Medieval Hagiography
BHL – Saint Ferreolus of Vienne & Saint Ferreolus of Limoges
Acta Sanctorum – Saint Ferreolus of Vienne & Saint Ferreolus of Limoges
The Cult of Saints in Late Antiquity Database (Vienne)
Art & Architecture
Index of Medieval Art – Saint Ferreolus of Limoges
Portail Biblissima – Saint Ferreolous of Vienne, although this is uncertain
POP : la plateforme ouverte du patrimoine (requires filtering)
The Saints in Art by Joseph Maria von Radowitz.
Emblems of Saints by Which They Are Distinguished in Works of Art by F. C. Husenbeth.
Nihil sub sole novum 