The great secret that all old people share is that you really haven't changed in seventy or eighty years. Your body changes, but you don't change at all. And that, of course, causes great confusion.
种树的最佳时间是20年前，第二好的时间是现在。
在这个喧嚣的世界里，一本书可以是一个安静的角落。
A mathematician's work is never done; there are always new questions to explore and new mysteries to uncover.
