Lives of the Saints by Sabine Baring-Gould.
The Liturgical Year by Dom Guéranger.
Pope Damasus’s Epitaph
“Nereus and Achilleus the martyrs joined the army and carried out the cruel orders of the tyrant, obeying his will continually out of fear. Then came a miracle of faith. They suddenly gave up their savagery, they were converted, they fled the camp of their evil leader, throwing away their shields, armor, and bloody spears. Professing the faith of Christ, they are happy to witness to its triumph. From these words of Damasus understand what great deeds can be brought about by Christ’s glory.” (quoted many places, searching for the source)
Art & Architecture
Sacred and Legendary Art volume II by Mrs. Jameson.
A Handbook of Christian Symbols and Stories of the Saints as Illustrated in Art by Clara Erskine Clement.
The Saints in Art by Joseph Maria von Radowitz.