Gw mau tau Catatan dari Goffredo I d'Altavilla

Houben, Hubert (translated by Graham A. Loud and Diane Milburn). Roger II of Sicily: Ruler between East and West. Cambridge University Press, 2002.

Curtis, Edmund. Roger of Sicily and the Normans in Lower Italy 1016-1154. G.P. Putnam's Sons: London, 1912.