Mule stables dotted the route. But the canal company ran out of money as faster railroads stole most of their business, and the C&O Canal never reached Pittsburgh and the Ohio River.

VOA: standard.2010.04.29

A good example to keep in mind is the idea of a mule.

大家可以记住一个很好的例子，那就是骡子。

麻省理工公开课 - 化学原理课程节选

A good example to keep in mind is the idea of a mule.

大家可以记住一个很好的例子，那就是骡子。

麻省理工公开课 - 化学原理课程节选