Richard Frye]: "Although the Tura in the Avestan Age were most probably Iranian, perhaps the memory of the struggles with aborigines played a part in the development of the epic.  Later, of course, the Turks conveniently took the role of the great enemies of Iran.  The extent of the influence of the Iranian epic is shown by the Turks who accepted it as their own history as well as that of Iran.  The Turks were so much influenced by this cycle of stories that in the eleventh century AD we find the Qarakhanid dynasty in Central Asia calling itself the 'family of Afrasiyab' and so it is known in the Islamic history”(R.N. Frye, The Heritage of Persia: The pre-Islamic History of One of the World's Great Civilizations, World Publishing Company, New York, 1963. Pg 40-41)"