And we need to continue to promote democracy and human rights beyond freedom's current frontiers, so that citizens everywhere are afforded the opportunity to pursue their dreams and live up to their own God-given potential,".

VOA: standard.2009.11.09

There were always battles and wars going on, on the boundaries, the frontiers of the Roman Empire, but within the center of the empire there was an amazing period of peace.

战争永远都在进行，在边界，罗马帝国边境，但在帝国中心却是一派和平盛世。

耶鲁公开课 - 新约课程节选

and, um, the class is called "Frontiers of Science."

那个课的名字叫《科学前沿》。

考试考砸了怎么办 - SpeakingMax英语口语达人

Some of those countries are really reliant on oil, ... so they really have to do-- they really should do a calculation of efficient portfolio frontiers.

有些国家过于依赖石油了，所以他们真的需要-,他们真的应该好好算一算,有效边界。

耶鲁公开课 - 金融市场课程节选