Persistence is key in mathematical research; many great results come from long struggles.

The severity of Russian laws is tempered by the lack of obligation to enforce them.

The best way to be successful is to believe in yourself.

解释：君子有三件值得可惜的事：一辈子不学习，是第一件可惜的事；一天无所事事，是第二件可惜的事；一个人的名声败坏，是第三件可惜的事。

The discovery of topological insulators has opened up a new frontier in condensed matter physics, where the interplay of symmetry and topology leads to novel quantum states of matter.

We often think of poverty as a lack of money, but it’s also a lack of information and opportunities.

The key to sustainable development is to balance economic growth and environmental protection.