No matter how complex or refined, all behavior is to be explained in terms of stimulus and response.
Escribir es una forma de explorar los límites de lo posible.
从n对观测值的样本中获得的相关系数的可能误差是sqrt((1-r²)/(n-2))。
The only service a friend can really render is to keep up your courage by holding up to you a mirror in which you can see a noble image of yourself.