The GHC documentation is written using DocBook 3.1, so the DTD line should be:
...
...
@@ -150,7 +150,7 @@ Used for variables, but not type variables.
</Sect1>
<Sect1><Title>Tables</Title>
<Sect1id="docbook-tables"><Title>Tables</Title>
<Para>
Tables are quite complicated to write in SGML (as in HTML, there are lots of fiddly tags), so here's an example you can cannibalise. In the spirit of the LaTeX short introduction I don't repeat all the markup verbatim; you have to look at the source for that.