Schadler, Peter (2017). "4". John of Damascus and Islam: Christian Heresiology and the Intellectual Background to Earliest Christian-Muslim Relations. Brill. p. 158. ISBN978-9004356054.
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referenceworks.brillonline.com
Weir, T.H.; Watt, W. Montgomery. "Ḥirāʾ". ใน Bearman, P.; Bianquis, Th.; Bosworth, C.E.; van Donzel, E.; Heinrichs, W.P. (บ.ก.). Encyclopaedia of Islam (2nd ed.). Brill Online. สืบค้นเมื่อ 7 October 2013.