I have come to realise that men are not born to be free.
Sometimes the most ordinary things are the hardest to explain.
Quality is remembered long after price is forgotten.
The beauty of instrumental variables is that they allow us to see the world in a new light.
宇宙中唯有两件事物是无限的:那就是宇宙的大小与人的愚蠢。而宇宙的大小我却不能肯定。