Here's the problem. How do I get to the nth- er, the k'th element in the list, in this case?

如何找到第n个元素呢-,在这里，如何找到第k个元素呢？

麻省理工公开课 - 计算机科学及编程导论课程节选

So sometimes what we do is introduce a little vector here called er.

通常我们的做法就是引入一个矢量 er

耶鲁公开课 - 基础物理课程节选

It is comforting to know that physicians such as yourself are still here, especially in the ER, who look for and identify those who may indeed be shopping, seeking, or otherwise abusing controlled substances.

FORBES: Fighting Prescription Drug Abuse With A National Online Database

Click here to find a child-friendly ER from the Joint Commission, which accredits hospitals.

CNN: How to find the best ER for your child