For All the Saints
- With links to other saints with whom Pope St. Sergius I was associated.
- http://www.saintpatrickdc.org/ss/0908.htm#serg

The Ecole Glossary
- Began the practice of singing the Agnus Dei during the Mass, and instituted the feast of the exaltation of the Cross.
- http://www2.evansville.edu/ecoleweb/glossary/sergiusi.html

Catholic Encyclopedia
- Pope St. Sergius I, d. 701 or 702.
- http://www.newadvent.org/cathen/13728b.htm

Popes Through the Ages
- Account of the pontificate of St. Sergius, from the book by Joseph Brusher.
- http://www.cfpeople.org/Books/Pope/POPEp84.htm