The council on educational technology in MIT has Been doing that for MIT with the help from a couple Of consultants who've actually volunteered their time.

麻省理工教育技术委员会,在一些顾问的帮助下做着这项工作,这些顾问自愿牺牲他们的时间参与其中。

麻省理工公开课 - 媒体、教育、市场课程节选

Here is the deal: What I am going to do is ask you-- this is all voluntary, you don't have to do it-- here's the deal.

交易是这样的，我要做的是要求你们-,纯属自愿，可以不做，交易是这样的。

哈佛公开课 - 幸福课课程节选