《新唐书·列传·卷一百四十二》
贞观十五年，皇帝册封李思摩为可汗，这才渡过黄河，设牙廷于漠南。
十五年，帝以李思摩为可汗，始度河，牙于漠南。
In the 15th year of the Zhenguan era, the emperor established Li Simo as the khan, and only then did he cross the Yellow River, and set up his headquarters in the desert to the south.