The Xueyantu (Seyanto, Se-yanto, Se-Yanto) or Syr-Tardush are an ancient Tiele people and khanate in central/northern Asia who are at one point vassals of the Gokturks, later aligning with China's Tang Dynasty against the Eastern Gokturks.
Xueyantuo starts from the Selenga River/Xueyanhe Rive, so the tribe name is Seyanto/Xueyantuo, Chinese Han characters undergo considerable revisions by the rises and falls of Chinese dynasties, so have many names, such as Xueyantuo, Xueyanhe, Xienianhe, Seyanto, Selenga, Selyanha, etc.
[NOTE: Loriano Belluomini claims that the correspondence Xueyantuo = Syr Tardush was rejected by modern historians.
It seems also ingenuous to link the name Xue-yantuo (according to Tongdian two different tribal names) with the Selenge river name].
