—— 请按键盘 空白键 开始游戏 ——

The beauty of instrumental variables is that they allow us to see the world in a new light.
I'm interested in all kinds of pictures, however they're made.
任何认真从事任何科学工作的人都会意识到,在科学殿堂的大门上方写着这样的文字:你必须有信仰。