"These difficult to reach populations frequently go underground and remain not visible to the medical delivery system,"

VOA: standard.2009.11.15

And my real answer is, go try it out, because obviously you can tell I frequently do this the wrong way and the TAs give me a hard time every time. John.

你可以，而我真正的答案是去试一试吧,因为很明显你可以发现我老是做错,而我的助教总是给我难堪，约翰。

麻省理工公开课 - 计算机科学及编程导论课程节选

I go to Amsterdam--not frequently, but I've been there ten or twelve times, or something.

我去过阿姆斯特丹,虽然并不常去,但也去过大概十次或者十二次

耶鲁公开课 - 欧洲文明课程节选