每个小镇都有自己的幽灵，每个幽灵都有自己的故事。
To be aware of the idea of social structure and to use it with sensibility is to be capable of tracing such linkages among a great variety of milieux.
PAC学习框架提供了一种正式的方法来分析学习算法的效率和有效性。
The world is full of obvious things which nobody by any chance ever observes.
