27 May – Saint John I

also identified as Pope Sixtus II with St. Felicissimus and St. Agapitus before Emperor Valerian

Modern Hagiography

Roman Martyrology

Lives of the Saints by Alban Butler.

Lives of the Saints by Sabine Baring-Gould.

The Liturgical Year by Dom Guéranger.

The Lives of Saints, with Other Feasts of the Year, According to the Roman Calendar by Peter Ribadeneira.

La vie des saints

Medieval Hagiography

BHL

Acta Sanctorum

The Cult of Saints in Late Antiquity Database

Liber pontificalis

Art & Architecture

Index of Medieval Art

Portail Biblissima

Wikimedia Commons

Medieval Religion Listserv – 2016 Dillon.

Post-Biblical Saints Art Index
Saints and their Attributes