Coal companies must fulfill their social responsibilities while pursuing economic benefits.

My biggest opponent is myself.

我认为生活中最重要的事情就是敢于梦想。

The beauty of instrumental variables is that they allow us to see the world in a new light.

语言中最具破坏性的短语是：“一直都是这样做的。”

如果一个国家期望在国民无知的情况下却拥有自由，那么这种期望无论在历史上，还是未来都绝不会实现。如果我们打算抵御无知和捍卫自由，每位美国人都有责任了解一件公共事务的来龙去脉。