《资治通鉴·唐纪·唐纪十一》
太宗派虞部郎中李道裕前往询问情状，并且对高昌来使说： 高昌这几年以来，不向我大唐进献贡品，不行藩臣的礼节，所设官职称号，均与我大唐一样，挖城掘沟，预备进攻。
上遣虞部郎中李道裕往问状，且谓其使者曰： 高昌数年以来，朝贡脱略，无籓臣礼，所置官号，皆准天朝，筑城掘沟，预备攻讨。
Emperor Taizong sent Li Daoyu, Minister of the Yubu, to inquire the general situation, and told the envoy of Gaochang: "Gaochang has not paid tributes, and has not observed the proper etiquettes of a vassal state. The official ranks and titles are all the same as ours, and you have dug moats to prepare for the attacks.