Bo Yang
The surname of Xueyantuo's khans is uncertain, although modern Chinese historian Bo Yang lists their surname as "Yishi" in his edition (also known as the "Bo Yang Edition") of the "Zizhi Tongjian", but without citing a source. It is possible that Bo was influenced by the "Tongdian", which refers to the Xueyantuo surname as "Yilitu" 壹利吐, "Yiliduo" 一利咄 as in "Cefu Yuangui", "Yilidie" 壹利咥 as in "New Book of Tang". Li Keyong's epitaph also records his alleged Xueyantuo ancestor's name as "Yidu" 益度.