↑Professor Richard Frye states:The Turkish speakers of Azerbaijan are mainly descended from the earlier Iranian speakers, several pockets of whom still exist in the region (Frye, Richard Nelson, «Peoples of Iran», in Encyclopedia Iranica).
↑« AZERBAIJAN , REPUBLIC OF»,., Vol. 3, Colliers Encyclopedia CD-ROM, 02-28-1996: «The original Persian population became fused with the Turks, and gradually the Persian language was supplanted by a Turkic dialect that evolved into the distinct Azerbaijani language.
↑Xavier Planhol, „Lands of Iran" in Encyclopedia Iranica. Excerpt: The toponyms, with more than half of the place names of Iranian origin in some areas, such as the Sahand, a huge volcanic massif south of Tabriz, or the Qara Dagh, near the border (Planhol, 1966, p. 305; Bazin, 1982, p. 28) bears witness to this continuity. The language itself provides eloquent proof. Azeri, not unlike Uzbek (see above), lost the vocal harmony typical of Turkish languages. It is a Turkish language learned and spoken by Iranian peasants.»(Encyclopedia Iranica, «Lands of Iran»)