《资治通鉴·宋纪·宋纪十》
了解一个人，本来就不是一件容易的事。我已经看错了他的内在品德，而崔浩又看漏了他的外在气质，这就是管仲之所以对鲍叔牙的死感到万分悲痛的真正原因啊！ 
夫人固未易知；吾既失之于心，崔又漏之于外，此乃管仲所以致恸于鲍叔也。 
It is not easy to understand a person in the first place. I have already made a mistake in seeing his inner character, and Cui Hao has missed his external qualities. This is the real reason why Guan Zhong was so saddened by Bao Shuya's death! 