[R] How to install older version of R?

[Pan, Jia-chiun/潘家群]

Dear list

        This is much like a linux problem, but I can't find any
reference for it. My OS is ubuntu 9.04 and a version of 2.9.2 of R has
been already installed in. Now, I need to install the version of 2.7.1.
I google a lot of websites and it seems like without a painless way
provided me to do it.
        If any one offers me some suggestions/reference, I will
appreciate.
		
                                             Jia-Chiun Pan