William, Count of Monte Sant'Angelo
According to the Chronica Montasterii Casinensis of Leo of Ostia, William (Guilelmus), whom Leo calls comes civitatis montis Sancti Michahelis archangeli ("count of the city of Saint Michael the Archangel"), made a donation to Montecassino in April 1100. The passage mentions his brother with no indication of his death, but he had perhaps already died by then, though he was not certainly dead until August 1103, probably dying 21 December 1102.
- Chalandon, Ferdinand. Histoire de la domination normande en Italie et en Sicile. Paris, 1907.
- Caravale, Mario (ed). Dizionario Biografico degli Italiani LXII Dugoni – Enza. Rome, 1993.
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- Cawley, Charles, "Sicily/Naples, Nobility (Conti d'Aversa)", Foundation for Medieval Genealogy, retrieved August 2012
- (Italian) Il Santuario di Monte Sant'Angelo nel Medioevo of Jean-Marie Martin