寻找互反律是数学史上的一个基本主题。
The most effective economic communities are founded on a shared ethical horizon, which includes a set of moral obligations that members of the community owe to one another.
数学研究是一次进入未知的旅程，每一次发现都为新的谜题打开了大门。
Life was simple before World War II. After that, we had systems.