Bresc, Henri (2003). "La Sicile et l'espace libyen au Moyen Age" [Sicily and the Libyan space in the Middle Ages] (PDF) (in French). Archived(PDF) from the original on October 9, 2022. Retrieved January 17, 2012. {{cite journal}}: Cite journal requires |journal= (help)
stanford.edu
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King, Peter (2015). "Peter Abelard". The Stanford Encyclopedia of Philosophy. Metaphysics Research Lab, Stanford University. Retrieved July 28, 2018.
storiamediterranea.it
Bresc, Henri (2003). "La Sicile et l'espace libyen au Moyen Age" [Sicily and the Libyan space in the Middle Ages] (PDF) (in French). Archived(PDF) from the original on October 9, 2022. Retrieved January 17, 2012. {{cite journal}}: Cite journal requires |journal= (help)