Last July President Barack Obama and his Russian counterpart, Dmitri Medvedev,agreed to work on a follow-on treaty to START-One.

VOA: standard.2009.12.07

So if you need the help of the notes it's in there but I would urge you to work through it on your own, and it's the following: let's start with the same path A, all right?

如果你需要帮助，可以去看讲义,但我还是希望你们自己去推导它,它是这样的，让我们从：,相同的路径A开始，好吗？

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