Reading is easy, thinking is difficult, and it is useless without them. (Franklin) In a sense, the history of science is a history of fantasy and failure, a history of big fools working clumsily and inefficiently. (Yin Yan, a temple man) Dig a well for learning. The deeper the well, the harder it is to get out. If you don't make up your mind to stick to it, how can you see the source (Zhang Jiugong)