《资治通鉴·宋纪·宋纪二》
赫连屈丐用蒸过的土建筑城墙，却被我灭掉了，这怎么在城的坚固不坚固呢？
屈丐蒸土筑城而朕灭之。岂在城也？
Helan Qugai used steamed earth to build the city wall, but I wiped him out. What does it have to do with whether the city is strong or not?