《资治通鉴·汉纪·汉纪三十三》
刘秀对太中大夫来歙说： 现在西州没有归附，公孙述自称皇帝，道路阻塞遥远，将领们正把力量用在关东。思量攻相西州的策略，不知道怎么办好。 
帝谓太中大夫来歙曰： 今西州未附，子阳称帝，道里阻远，诸将方务关东，思西州方略，未知所在，奈何？ 
Liu Xiu said to Lai She, the Grand Master of the Palace: "Now Xizhou has not yet surrendered, Gongsun Shu has declared himself emperor, the roads are long and blocked, and the generals are focusing their efforts on Guandong. When considering the strategy to attack Xizhou, I do not know what to do".