Anonymous Monk of Whitby. The earliest life of Gregory the Great, 1968.
Catholic Encyclopedia www site, 20 Sept. 2007 Pope St. Gregory I page (consecrated pope 3 Sept. 590)
Dekkers, E. Voordrachten over de heilige Gregorius der Grote, 1986.
Gregory I, Pope. Vioi agnōstōn askētōn, 1988 p. 5: (Hagiou Grēgoriou tou Megalou Papa Rōmēs) p. 15 (Ho hagios Grēgorios ho Megas (540-604))
Wikipedia, 26 January 2011 (Pope Gregory I (Latin: Gregorius I) (c. 540-12 March 604), better known in English as Gregory the Great, was pope from 3 September 590 until his death)