《资治通鉴·唐纪·唐纪五十七》
王士元等人答称： 成德王承宗和淄青李师道同谋策划派遣刺客暗杀武元衡，我们受李师道的指派赶赴京城，不料来晚，误了约定的日期。听说成德人已经把武元德杀害，于是，我们就把功劳据为己有，为的是回去报功领赏。
元略问其故，对曰： 恒、郓同谋遣客刺元衡，而士元等后期，闻恒人事成，遂窃以为己功，还报受赏耳。
Wang Shiyuan and others replied: Chengde Wang Chengzong and Ziqing Li Shidao conspired to send assassins to assassinate Wu Yuanheng. We were sent to the capital by Li Shidao, but we were late and missed the agreed date. We heard that the Chengde people had killed Wu Yuande, so we took credit for it in order to go back and claim credit for reward.