Wei Zheng
Hamilton (1962) and Zuev (2002) saw the first reference to the Chigil as 職乙 ("Zhiyi"), whose Middle Chinese pronunciation was reconstructed by Zuev as "tšįək-iət", as a Tiele tribe mentioned in Book of Sui, compiled by Wei Zheng. However, the original manuscript contains no punctuation, so different scholars read and reconstruct the ethonyms differently: for example, 薄落職乙咥 may also be read as "Boluozhi" and "Yidie"