Retrospective studies of different populations could not control for differences in wealth and culture.
Retrospective studies of different populations could not control for differences in wealth and culture.
对不同族群所做的回顾性研究，无法解决经济与文化条件上的差异。
Retrospective studies of different populations could not control for differences in wealth and culture.
对不同族群所做的回顾性研究，无法解决经济与文化条件上的差异。