The main archive is at Google groups, AFAIK. I vaguely recall that
they have some procedure for requesting that an item be removed. Look
at their help, and look for contact info.

bob

Basically, one should consider it impossible to have a post removed
from Usenet.  The reason is that there is a separate copy on each
newsserver - a number that would be in the 100's of thousands the last
I heard - and you would have to deal with them each individually.
Even then, most will not remove posts without a court order.

Someone may tell you to try to cancel it.  Don't.  Not only is trying
to cancel a post not your own considered abuse of the net, but it
won't work.  Most of the major servers either don't honor cancels or
honor only specific ones that you have no chance of faking.

Provided the post contains the entire item and not just an excerpt
posted for comment, see an attorney about copyright infringement.

In my personal opinion?  I'm pretty sure I know which post is the
problem.  Give it a month or so.  Your sales might even increase; the
price isn't much for a clean copy.

Carol