Sustainability isn't a buzzword; it's the foundation of modern resource extraction.

书籍是反映我们挣扎的镜子。

Freedom is a condition of mind,and the best way to secure it is to breed it.

书是一面镜子：如果一只猿猴往里看，使徒不太可能往外看。

数学的本质在于它的自由。