So he thinks it makes a lot of sense for today's barbers to act as "health care extenders" by sharpening their skills.

VOA: special.2010.10.27

That's why there's a lot of emphasis on sharpening your teeth by doing this class of problems.

这就是为什么强调要通过解决这些问题,来提高你的能力

耶鲁公开课 - 基础物理课程节选