幸福者的世界与不幸者的世界是完全不同的。
The best way to cheer yourself up is to try to cheer somebody else up.
Mathematics advances not by the efforts of individuals alone but through the collective work of generations.
When I look at the world I'm pessimistic, but when I look at people I am optimistic.
Solving a problem simply means representing it so as to make the solution transparent.