《水经注·卷四》
正像宫之奇所说的，虞、藐两国互相依存，唇亡齿寒，貌国一亡，虞国也灭了。
即宫之奇所谓虞，虢其犹辅车相依，唇亡则齿寒，虢亡，虞亦亡矣。
As said by Gong Zhichi, the two countries of Yu and Miao depended on each other, faced with the same fate. With the collapse of Miao, Yu was also destroyed.