The Kingdom of Qocho survived as a client state of the Mongol Empire but was conquered by the Muslim Chagatai Khanate, which conquered Turfan and Qomul and Islamized the region. Old Uyghur then became extinct in Turfan and Qomul.
Qocho, the Uyghur kingdom created in 843, originally used the "runic" Old Turkic alphabet with a "anïγ" dialect. The Old Uyghur alphabet was adopted from local inhabitants, along with a "ayïγ" dialect, when they migrated into Turfan after 840.[7]
Chén Zōngzhèn & Léi Xuǎnchūn. 1985. Xībù Yùgùyǔ Jiānzhì [Concise grammar of Western Yugur]. Peking.
Clauson, Gerard (April 1965). "Review An Eastern Turki-English Dictionary by Gunnar Jarring". The Journal of the Royal Asiatic Society of Great Britain and Ireland (1/2). Royal Asiatic Society of Great Britain and Ireland. JSTOR25202808.