《战国策·韩一·郑彊之走张仪于秦》
为此郑强西去秦国求见秦王说： 张仪派人向楚国献上上庸之地，所以楚王派使臣我两次拜见大王。 
故因而请秦王曰： 张仪使人致上庸之地，故使使臣再拜谒秦王。 
For this reason, Zheng Qiang went west to the State of Qin and asked to meet the King of Qin, saying: "Zhang Yi will send someone to offer the Shangyong Place to the State of Chu, so the King of Chu sent envoy to pay a visit to your Majesty twice."