Sometimes he did not even keep a copy of his book.

VOA: special.2010.01.10

I think these extra pictures sometimes they're helpful, sometimes they just make the book cost a lot more.

我想这些补充的图片有时是有用的,有时仅仅是把书价抬高了一点

耶鲁公开课 - 基础物理课程节选

But, I think what most of you, actually having MIT come to MIT, have probably realized is sometimes it's nice to major in a science, because you can't just pick up a reaction and do it in your kitchen on the weekend, where as you can sometimes join a book group and do that.

但我认为对你们大多数人来说,既然来了,可能已经意识到最好是主修一门科学,因为你不能在你,周末的时候在厨房里做化学实验,然后你就可以参加一个读书俱乐部。

麻省理工公开课 - 化学原理课程节选

Aristophanes' play sometimes is even included in certain editions of the book you're reading like this one it has the edition of Aristophanes' Clouds in it along with the Apology and Crito.

亚里斯多芬尼斯的剧作有时,也会包含在,你们所读的特定版本书中，像这本,它内含亚里斯多芬尼斯的《云》,还有《苏格拉底自辩篇》和《克里托篇》

耶鲁公开课 - 政治哲学导论课程节选