↑(anglès) Geary, Patrick J. Before France and Germany. Oxford University Press: 1988
↑(anglès) Halsall, Guy (2003). Warfare and Society in the Barbarian West 450-900. London: Routledge. ISBN 0-415-23939-7, p. 226.
↑(anglès) Mastnak, Tomaz (2002). Crusading Peace: Christendom, the Muslim World, and Western Political Order. University of California Press. ISBN 0-520-22635-6, p. 101.