The two presidents met for the first time on the sidelines of the G-20 economic conference in London in early April and set in motion what Clinton says is an effort to raise the frequently contentious U.S.-Russian relationship to a higher level.

VOA: standard.2009.05.07

Let's start with our first triumph will be motion in 1D.

我们先从一维问题开始

耶鲁公开课 - 基础物理课程节选

Let's start with our first triumph will be motion in 1D.

我们先从一维问题开始

耶鲁公开课 - 基础物理课程节选