The beauty of instrumental variables is that they allow us to see the world in a new light.
法律,在其最一般的意义上,是事物本质产生的必要关系。
I don't know where the limits are, but I would like to go there.
The greatest happiness is to transform one's feelings into action.
作家是反映社会灵魂的镜子。
We must balance economic growth with environmental responsibility; they are not mutually exclusive.