^ abWilliams, Hywel (2005). Cassell's Chronology of World History. London: Weidenfeld & Nicolson. pp. 113–114. ISBN0-304-35730-8.
^ abJohn France. Victory in the East (Book extract). Godfrey was almost certainly present in support of Henry IV at the battle of Elster in 1080 (sic 1085... an error or typo), when the forces of the anti-king Rudolf triumphed on the field only to see their victory nullified because Rudolf was killed
^Picard C. (1997) La mer et les musulmans d'Occident au Moyen Age. Paris: Presses Universitaires de France.