For All the Saints: Four Crowned Martyrs
- Katherine I. Rabenstein attempts to sort out the claimants to the title of the Four Crowned Martyrs.
- http://www.saintpatrickdc.org/ss/1108.htm#four

Catholic Encyclopedia: Four Crowned Martyrs
- The Four Crowned Martyrs are actually two groups, with a total of nine or ten martyrs. The first five were masons or sculptors in Pannonia, martyred in 305. The second was a group of four martyrs, names unknown. They have been venerated since the fourth c
- http://www.newadvent.org/cathen/06163a.htm