Works about Gregory the Great

March 12. -- St. Gregory of Great -- from from Lives of the Saints with Reflections for Every Day of the Year
Catholic Encyclopedia, Volume 6: Fathers of the Church-Gregory XI -- from Herbermann, Charles George (1840-1916)
Gregory I, St. (c. 540-604) -- from Wikipedia Article
Gregory the Great -- from The New Schaff-Herzog Encyclopedia of Religious Knowledge