Redirect with SOME Querystring Parameters Maintained?

[AlexGrim]

I am trying to do a Redirect with SOME Querystring Parameters Maintained. I already know how to do a redirect with ALL parameters maintained, or with NO parameters maintained, but in this particular case, i need only ONE of them dropped.

For example, my old links for my old system were something like:
http://linuxintro.com/?a=Article_Page_Display&id=900072752405

But now they are like this:
http://linuxintro.com/?a=WCMS_Page&id=900072752405

So i need to drop the "a" parameter, but keep the "id" parameter, so that i know which article to display.
Thanx

[AlexGrim]

Solved:

RewriteCond %{QUERY_STRING} a=Article_Page_Display&id=(.*) [NC]
RewriteRule ^(.*)$ http://LinuxIntro.com/\?a=WCMS_Page&id=%1 [R=301]