This is how to add my extensions to "sgmltools".
The paths might of course vary in your distribution.

- link/copy  ./linuxdoc-ea.dtd  to  /usr/lib/sgml-tools/dtd/linuxdoc-ea.dtd

- link/copy  ./linuxdoc-ea      to  /usr/lib/sgml-tools/dist/linuxdoc-ea

  (the empty file "mapping" in "linuxdoc-ea/html" is needed,
  but dont know why)

- add the following to /usr/lib/sgml-tools/dtd/catalog

  <-- for own development, internal use only -->
  DOCTYPE "LINUXDOC-EA"      "linuxdoc-ea.dtd"

