(Inggris) J. Ghellinck (1911), "Peter Lombard", The Catholic Encyclopedia, Transcribed for New Advent by Herman F. Holbrook, New York: Robert Appleton Company
(Inggris) Daniel Kennedy (1912), "Sacraments", The Catholic Encyclopedia. Vol. 13, Transcribed for New Advent by Marie Jutras., New York: Robert Appleton Company