XHTML 1.1 2nd Ed. DTD?

[Martin Kliehm]

Thanks for publishing the revised edition for XHTML 1.1, it does a much 
better job explaining how custom DTDs can be constructed.

However I seem to be unable to find the current XHTML 1.1 DTD. I wanted 
to check whether the target module (and possible the iframe module as 
invalid item number 2) is back in the core set of modules.[1]

I'd appreciate if you could provide a URL where I can download the DTD.

Thanks,
  Martin

[1] http://lists.w3.org/Archives/Public/www-html-editor/2007JanMar/0033.html