I advertise on AdCenter in CA, US, and UK 'markets'. For each market I 'allow' traffic from every English speaking country.

Now I want to advertise in German. I want to advertise in the DE 'market', and allow traffic from Germany to see these ads.

How do I do this? I read this post [webmasterworld.com...] and it suggested that I have to go through Yahoo!. Is that true? If so, is there anything special I have to do with Yahoo?

Thanks!