周書
Primary Chinese sources ascribed different origins to the Ashina tribe. Ashina were first attested to 439, as reported by the "Book of Sui": on October 18, the Tuoba ruler Emperor Taiwu of Northern Wei overthrew Juqu Mujian of the Northern Liang in eastern Gansu, and 500 Ashina families fled northwest to the Rouran Khaganate near Gaochang. According to the "Book of Zhou", "History of the Northern Dynasties", and New Book of Tang, the Ashina clan was a component of the Xiongnu confederation. but this is contested. Göktürks were also posited as having originated from an obscure Suo state (索國), north of the Xiongnu. According to the "Book of Sui" and the "Tongdian", they were "mixed barbarians" (; "záhú") from Pingliang.