理论上，理论和实践之间没有区别。但实际上，是有区别的。
In theory, there is no difference between theory and practice. But, in practice, there is.
History is not just about kings and battles—it's about the people who lived through it.
Combinatorics is the art of counting without counting.
在爱情中我们都是傻瓜。
It seems to me that if you or I must choose between two courses of thought or action, we should remember our dying and try so to live that our death brings no pleasure to the world.
了解这个世界就是爱它，而爱它就是为它哀伤。