在观察性研究中，我们常常不得不依赖于无法直接检验的假设。
"In observational studies, we often have to rely on assumptions that are not directly testable."
The power of accurate observation is commonly called cynicism by those who have not got it.
Quality should never be compromised, even in the face of challenges.
A true friend is the one who holds your hand and touches your heart.