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(anglès) William Muir, The Caliphate, its rise, decline and fall, Chapter LXXVIII, 640-656 A.H., Al-Musta'sim, last of the Caliphs, Hulagu takes Bagdad, Caliph put to death, End of 'Abbasid Dynasty
answering-islam.org
(anglès) E. M. Wherry, A Comprehensive Commentary On The Quran, Of the Arabs before Muhammad; or, as they express it, in the Time of Ignorance; their History, Religion, Learning, and Customs
