《新唐书·列传·卷一百四十四》
懿宗咸通年间，契丹王习尔之两次派使者入朝，部落渐强。
咸通中，其王习尔之再遣使者入朝，部落浸强。
In the years of Emperor Yizong's Xian Tong reign, Qidan King Xi E Zhi sent envoys to the court twice, with the tribe gradually growing stronger.