^Bernard Lewis (1991), "The Political Language of Islam", University of Chicago Press, pp 314. "The last and most nearly successful of the Iranian movements, however was that of Babak, who established his independence in Adharbayjan early in al-Mamun's reign."
^F. Daftary (1999) Sectarian and National Movements in Iran, Khurasan and Transoxania During Umayyad and Early 'Abbasid Times In History of Civilizations of Central Asia, vol. IV, part One, ed. M. S. Asimov and C. E. Bosworth. Paris: UNESCO Publishing, pp. 41–60. excerpt from pg 50: "The activities of the Khurammiya reached their peak in the movement of Babak al-Khurrami, whose protracted rebellion based in north-western Iran seriously threatened the stability of the Abbassid caliphate.... This revolt lasting for more than twenty years, soon spread from Azerbaijan (North/West Iran) to western and central parts of Iran.
^Kathryn Babayan, "Mystics, monarchs, and messiahs ", Harvard CMES, 2002. pg 138: "Babak revolted in Azerbaijan (816–838), evoking Abu Muslim as a heroic symbol..and called for a return to the Iranian past"
