Chalandon, 1926, p. 187. (EN) Ferdinand Chalandon, The Norman Kingdom of Sicily, in J.R. Tanner, C.W. Previte-Orton e Z.N. Brooke (a cura di), The Cambridge Medieval History: Contest of empire and papacy, Cambridge University Press, 1926, pp. 184-207.
Pacaut, 2002, p. 784. (EN) Marcel Pacaut, Innocent II, in Philippe Levillain (a cura di), The Papacy An Encyclopedia, vol. 2: Gaius-Proxies, Routledge, 2002, pp. 783-785.