工具变量的美妙之处在于它们让我们以新的视角看世界。

Hope is a good thing, maybe the best of things, and no good thing ever dies.

The artist must be in his work as God is in creation, invisible and all-powerful; one must sense him everywhere but never see him.

生活中最大的荣耀不在于从不跌倒，而在于每次跌倒后都能站起来。

志村簇的研究证明了几何直觉的力量。