found: Burtius, N. Musices opusculum, 1983:p. 12 (Guido) p. 25 (Guido d'Arezzo)
found: LC data base, 5-1-89(hdg.: Guido Aretinus, d. 1050?; usage: Guido; Guidonis Aretini ...; ... Guidonis d'Arezzo; ... Guidos von Arezzo)
found: Baker, 7th ed.(Guido d'Arezzo (Guido Aretinus); b. ca. 997; d. date uncertain; the often cited d. date 5-17-1050 is without foundation)
found: New Grove(Guido of Arezzo (Aretinus), b. ca. 991 or 2; d. after 1033; music theorist and pedagogue; another possible b. date is between 994 and 998)
found: Guido, d'Arezzo. Micrologus, 1993:t.p. (Gui d'Arezzo)
found: Guido Monaco, c2000:p. 7 (Guido d'Arezzo)