A proof is a way to convince yourself and others that something is true.
有利的时机和气候不如有利的地势,有利的地势不如人的齐心协力。
经济模型的价值在于其解释和预测的能力。
人们说逝者总是在俯视着我们。但我们从不回望。
I was neat, clean, shaved and sober, and I didn't care who knew it.