But advisers say these can also be difficult sometimes for foreign students to get.

VOA: special.2009.05.28

Now the intervention studies are stronger methods than the epidemiology studies but they're also more difficult studies to do.

相比传染病学研究,干预性研究更有效,但也更难执行

耶鲁公开课 - 关于食物的心理学、生物学和政治学课程节选

but it's also very difficult.

但是它也很难学。

要继续努力 - SpeakingMax英语口语达人

But he was also extremely large and difficult to control.

VOA: special.2009.02.23

but he's also insisting that this is an incredibly difficult, if not impossible, moment of thought.

但他同时坚持，如果可能，这对思维来说也是一个极其艰难的时刻。

耶鲁公开课 - 文学理论导论课程节选

What makes this enterprise difficult but also riveting is that moral and political philosophy is a story and you don't know where the story will lead.

这一过程会充满挑战又引人入胜,因为道德与政治哲学就好比一个故事,你不知道故事将会如何发展。

耶鲁公开课 - 公正课程节选