Description of problem:
The current docbook-dtds package does not include version 4.3 of the
DocBook XML DTD. (Maybe SGML DTD, too. Haven't checked.)
The docbook-slides package that I'm building is supposed to depend on
V4.3, but it's no problem to patch it to depend on V4.2. This is how I
noticed that V4.3 was missing.
You probably missed the release of V4.3 because the DocBook TC was
having problems posting materials on the OASIS site, so Norm Walsh was
putting the new versions on http://docbook.org, instead of at OASIS.
Version 4.3 is available at http://docbook.org/xml/4.3/docbook-xml-4.3.zip