"Four years looking back, we've had some students will do Hanukkah, some Kwanzaa,some Christmas.

VOA: special.2009.12.24

Well, this allows us to try to go back and explain some phenomena that over the years, mounting evidence was building that couldn't be explained.

好了，这个可以使得我们,返回去然后去解释一些，以前逐年积累的未能解释的现象,我们下节课将讨论。

麻省理工公开课 - 化学原理课程节选

Some of the coral dated back about four thousand years.

VOA: special.2010.08.10

A conflict the U.S.fought and lost some 40 years ago has come back to haunt a young president, his advisors,his generals, and the country he governs.

VOA: standard.2009.09.09