"In observational studies, we often have to rely on assumptions that are not directly testable."
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。
The word was my country, and of that I was deprived.
质量是我们产品的灵魂，诚信是我们事业的根基。
The greatest economic transformations often begin with small, deliberate steps.
"I write because I cannot live without writing."