You must not think that what is hard for you to master is humanly impossible； and if it is humanly possible， consider it to be within your reach.

In mathematics, the art of proposing a question must be held of higher value than solving it.

书籍是想象力的钥匙，而想象力是未来的钥匙。

生命中最伟大的事情是保持心灵年轻。