《元史·列传·卷四十六》
子贞单骑到济南考察李王的形势，对丞相史天泽说： 王拥兵从益都而来，坐守济南孤城。宜增筑外城，防他突围。彼粮尽援绝，不攻自破。 
子贞单骑至济南，观璮形势，因说丞相史天泽曰： 璮拥众东来，坐守孤城，宜增筑外城，防其奔突，彼粮尽援绝，不攻自破矣。 
Zi Zhen went to Jinan alone to investigate the situation of King Li. He said to the prime minister Shi Tianze: "King Li led his troops from Yidu and is now defending the isolated city of Jinan. We should build an outer city to prevent him from breaking out. When his food runs out and reinforcements are cut off, he will be defeated without a fight."