Ludger of Utrecht
- Hagiographical essay, with links to other saints with whom Ludger is associated.
- http://www.saintpatrickdc.org/ss/0326.htm#ludg

Lives of the Saints: St. Ludger
- Entry for this bishop of Munster, Apostle of Saxony, from Alban Butler's Lives of the Saints.
- http://www.ewtn.com/library/MARY/LUDGER.HTM

Catholic Encyclopedia: St. Ludger
- Also known as St. Lüdiger, or Liudger. Biography of this missionary, the first bishop of Munster, who died in 809.
- http://www.newadvent.org/cathen/09415a.htm