Olof Heilo: Seeing Eye to Eye: Islamic Universalism in the Roman and Byzantine Worlds,7th to 10th Centuries, Wien 2010 med referanse til Robert Høyland:, Seeing Islam as Others Saw, side 120 – http://othes.univie.ac.at/10921/1/2010-07-21_0549369.pdf. Besøkt 26.1.2012.
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Wells, Colin (2004-02-17). "Yehuda D. Nevo, Judith Koren, Crossroads to Islam: The Origins of the Arab Religion and the Arab State.". Bryn Mawr Classical Review. http://ccat.sas.upenn.edu/bmcr/2004/2004-02-33.html. 14 December 2006.