无限小在自然中的作用是无限大的。
A good mechanic is not merely a man who files and hammers, but one who can originate and perfect.
The most important thing is to be able to think like an economist, to see the world through that lens.
The only thing I know is that I paint because I need to, and I paint whatever passes through my head without any other consideration.
There is no better teacher than history in determining the future……There are answers worth billions of dollars in a history book.