每个回声都包含着它所处空间的历史。

Success is not final, failure is not fatal: it is the courage to continue that counts.

We read to know we are not alone.

Always demand a deadline. A deadline weeds out the extraneous and the ordinary. It prevents you from trying to make it perfect， so you have to make it different. Different is better.

追求数学知识是一段永无止境的旅程。