Catholic Encyclopedia
Pope St. Sixtus I. Also spelled Xystus. Martyr, reigned for ten years in the very early part of the second century.
For All the Saints
Short biography of Pope St. Sixtus I.
Popes Through the Ages
Profile of St. Sixtus I, from the book by Joseph Brusher.
The Ecole Glossary
Brief article on Pope St. Sixtus I, by Karen Rae Keck.