But Amy Ramirez and Cheryl Gilman both say foreign students should understand that visa rules change often.

VOA: special.2009.07.02

We need to change our rules just slightly.

我们需要稍稍改变我们的规则。

麻省理工公开课 - 化学原理课程节选

The ones that are accepted in public speech change through the years as social rules change.

VOA: special.2010.02.14

"We have 192 countries in the framework convention on climate change and one of them wants to have separate rules,".

VOA: standard.2009.11.04