Gw mau tau Catatan dari Guillaume II d'Angoulême

B. S. Bachrach. "The Angevin Strategy of Castle Building in the Reign of Fulk Nerra, 987–1040." The American Historical Review 88 (1963): 533–60.

B. S. Bachrach. "Toward a Reappraisal of William the Great, Duke of Aquitaine (995–1030)." Journal of Medieval History 4 (1979): 11–21.