"The problem with that body of research is that it's difficult to interpret because obviously people with existing mental health problems use cigarettes to self-medicate."

VOA: standard.2010.06.15

Well, I talked about the problem of using plasmids in gene therapy, that it's very difficult to get them into cells.

我们之前讨论过,基因治疗中运用质粒的问题,质粒本身极难进入细胞

耶鲁公开课 - 生物医学工程探索课程节选

Part of the problem with using operant conditioning with babies is it's difficult to get them to behave in any systematic way.

应用操作性条件作用的部分问题在于,很难使婴儿们按照系统的方式行动

耶鲁公开课 - 心理学导论课程节选

In many ways for Aristotle as it is for every student of politics the most serious the most difficult issue one confronts is the problem of faction.

从很多方面看来，无论是对亚里士多德,还是每位政治系的同学而言,最令人最感严肃,与严重的问题,是派系的问题。

耶鲁公开课 - 政治哲学导论课程节选