《资治通鉴·唐纪·唐纪五》
当初，处罗可汗与刘武周内外呼应，侵犯并州；高祖派太常卿郑元前去晓以祸福，处罗不听。
初，处罗可汗与刘武周相表里，寇并州；上遣太常卿郑元璹往谕以祸福，处罗不从。
At the beginning, Chuluo Khan and Liu Wuzhou echoed each other from inside and outside, invading Bingzhou; Emperor Gaozu sent the minister of the imperial rituals, Zheng Yuan, to explain the harm and good fortune to him, but Chuluo did not listen.