It is well known that the oldest existing complete literary work of a Mussulman Turk, the Qudatqu Bilik or Qutadghu Bilik, was composed in 462 H. (a.d. 1069–70) by Yūsuf Khāṣṣ Ḥājib, a native from Bālāsāghūn, on the River Chu, for a Khān residing in Kāshghar who is called “Mashriq Maliki Tabghach Khani Malik Bughra Khan” (King of the East, Khan of China, the King Bughra Khan), “Tabghach Qara Bughra Khanlar Khani” (the Chinese Qara Bughra, the Khan of Khans), “Tabghach Ulugh Bughra Khan” (the Chinese, the great Bughra Khan), even more simply “Ordukent Khani Beg” (the Khan of the court-town, that is Kashghar, the prince). The statements concerning the chronology of the Kashghar kings of the eleventh century are very vague and scanty, and are not supplied by numismatic evidence; therefore it is not an easy task to ascertain who was the king mentioned by Yūsuf. There can be no doubt that he belonged to the dynasty of the Ilek Khāns. The chief authority on the history of that dynasty has been for all Muhammedan and European scholars the great work of Ibn al-Athīr, especially the statements given under the year 408 H. We are told by Ibn al-Athīr that Arslān Khān, son of Qādir Khān Yūsuf, King of Kāshghar, Khotan, and Bālāsāghūn, was deposed by his brother Bughra Khān and taken prisoner; Bughrā Khān was some time later poisoned by his wife, who put to death Arslān Khān also, in 439 H. Bughrā Khān ruled only fifteen months and was succeeded by Ṭoghrul Khān, son of Yūsuf Qadir Khāan (that is, by his brother), who ruled sixteen years (until 456 or 457). His son, Ṭoghrul-tagīn, was deposed after two months by “Hārūn Bughrā Khān, brother of Yūsuf Ṭoghrul Khān and son of Ṭafghāch Boghrā Khān” (?); Hārūn Bughrā Khān passed (‘abara) Kāshghar, made Hārūn (? mistake for Ṭoghrul-tagīn) prisoner; the army of the latter submitted to him, and he took possession of Kāshghar, Khotan, and the neighbouring districts to Bālāsāghūn, where he reigned twenty-nine years and died in 496. These statements can, of course, not be quite correct; if Bughrā Khān Hārūn was the brother of Ṭoghrul Khān, he must have been a son of Yūsuf Qadír Khān, and is, in fact, called so by Ibn al-Athīr himself on the previous page. The reigns mentioned by Ibn al-Athīr, and said to have extended from 439 to 496 (fifty-seven years), do not cover all that time, but nearly ten years less. We know, indeed, from an earlier author, Abu-I-Faḍl Baihaqī, that the first Bughrā Khān (called by Ibn al-Athīr Maḥmud) died not in 439 but in 449. Bughrā Khān Hārūn must have reigned in this case from 467 to 496, Ṭoghrul Khān from 451 to 467; the Qudatqu Bilik, composed in 462, was therefore written in the reign of Ṭoghrul Khān, but Bughrā Khān seems to have been a co-regent of his brother; Ibn al-Athīr speaks of the war made by the two brothers against Shams al-Mulk, Khān of Samarqand. Therefore it was quite natural to come to the conclusion that the Bughrā Khān mentioned by Yūsuf Khāṣṣ Ḥājib was Bughrā Khān Hārūn ibn Yūsuf, and such an opinion has been expressed in my article “Bughrā Khān” in the Encyclopædia of Islām.