By used books. They have the same words as the new ones. Also libraries.

气候变化不是一个遥远的问题——它已经到来，而森林是我们的第一道防线。

我总是相信，只要我尽力了，结果自然会随之而来。

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

正义的代价是永恒的公开。

守住嘴巴，就跟拴紧瓶口一样。克制欲望，就像防守城池一般。