《旧唐书·本纪·卷十八》
皇上下诏，回鹘进犯边境并逐渐侵入内地，对他们是进攻还是防守，怎样才算是合理办法，令太子少师牛僧孺、陈夷行与公卿大臣们集体商议可否实行，以奏闻皇帝。
诏以回纥犯边，渐浸内地，或攻或守，于理何安？令少师牛僧孺、陈夷行与公卿集议可否以闻。
The emperor ordered that the Huige had invaded the border and gradually penetrated inside the country. Whether to attack or defend them, and how to do so in a reasonable way, he ordered the Crown Prince Shao and the minister Niu Sengru, Chen Yixing, and the ministers to discuss it together to see if it could be done, and then report to the emperor.