It is mixed for about two hours with some common chemicals and then allowed to cool.

VOA: special.2011.07.25

Now for now, its hard to argue that this is a good thing but it's a common thing.

现在，不好争论这是一个好事情,但这是一个通常的事情。

哈佛公开课 - 计算机科学课程节选

It is mixed for about 2 hours with some common chemicals and then allowed to cool.

VOA: special.2009.01.26

Is it possible for us to join hands in common effort?

VOA: special.2009.06.05