屋顶上的天空,如此蔚蓝,如此宁静!
开玩笑是件严肃的事情。
The only real mistake is the one from which we learn nothing.
To enjoy freedom we have to control ourselves.
The human heart is a complex and often contradictory thing.
心理学的方法必须像自然科学的方法一样精确。
The most important thing is to have a vision of what you want to do and then to have the persistence to carry it out.
在数学中,提出问题的艺术必须比解决问题更有价值。