《战国策·燕一·燕文公时》
现在如果让弱小的燕国做先锋，而强大的秦国做后盾，从而用天下的精兵进攻齐国，这与吃乌喙来充饥是一个道理。 
今使弱燕为雁行，而强秦制其后，以招天下之精兵，此食乌喙之类也。 
If you let the weak Yan be the vanguard and the powerful Qin be the rear guard, and then use the elite soldiers of the world to attack Qi, it would be like eating aconite to quench your thirst.