《新唐书·列传·卷一百四十》
统叶护可汗来求婚，皇帝与群臣商议 ：西突厥离我远，如有缓急不可倚仗，能与他们联姻么？ 
统叶护可汗来请昏，帝与群臣谋： 西突厥去我远，缓急不可杖，可与昏乎？ 
Khan Tongyehu came to ask for a marriage. The emperor had a discussion with his ministers: Western Turk is far away from me, will they be reliable when it comes to adversity, could we intermarry with them?