We've done price elasticity studies, and the answer is always that we should raise prices. We don't do that, because we believe -- and we have to take this as an article of faith -- that by keeping our prices very, very low, we earn trust with customers over time, and that that actually does maximize free cash flow over the long term.

要理解世界，你必须首先寻求理解自己。

计算复杂性理论的发展向我们展示了并非所有问题都是平等的。

我学得越多，就越意识到自己不知道的还有多少。

The future of coal lies not in its quantity but in how cleanly and efficiently we can use it.

今天很残酷，明天更残酷，后天很美好。