"The act of writing is an act of optimism. You wouldn't take the trouble to do it if you felt it didn't matter."

Never let your sense of morals prevent you from doing what is right.

成功辨识的关键是找到一个足够灵活的模型结构，以捕捉系统的基本特征，同时又足够简单，可以从现有数据中估计出来。

一个理论的优雅不仅在于其数学表述，还在于其在一个统一框架下连接不同现象的能力。