Modern Hagiography
Bibliotheca Sanctorum – Saint Soter & Saint Caius.
Martyrologium Romanum
Roman Martyrology
Sanctorale Catholicum
Lives of the Saints by Alban Butler – Soter & Caius.
The Liturgical Year by Dom Guéranger.
Character Calendar
Pictorial Lives of the Saints
La vie des saints
Medieval Hagiography
BHL – Soter, Caius
Acta Sanctorum – Soter, Caius
The Cult of Saints in Late Antiquity Database – Soter, Caius
Liber pontificalis – Soter, Caius
The Golden Legend (Pope Caius)
Breviarium Romanum – Latin & English
Writings by Saint Soter
Ad episcopos Italiae
Decretalia de fede
Writings by Saint Caius
Documenta Catholica Omnia
Art & Architecture
Index of Medieval Art – Soter, Caius
– El Escorial, Real Biblioteca, Cod. Vitrinas 17, folio 5r & 5v:
Catalogo generale dei beni culturali – San Caio, San Sotero
BeWeB – San Caio, San Sotero
Portail Biblissima – Saint Caius and also
Wikimedia Commons – Saint Soter & Saint Caius.
Martyrdom of Pope Caius
The Sistine Chapel, North Wall
Saint Soter
In situ
Die Sixtinische kapelle
Entrance Wall, Sistine Chapel
In situ
Post-Biblical Saints Art Index – Caius
Post-Biblical Saints Art Index – Soter
Saints and their Attributes
Saints and their Emblems
Saints and their Emblems
The Saints in Art by Joseph Maria von Radowitz – Caius.
Nihil sub sole novum 
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