The current version of niceSgml2Html is v0.4 . This version works with sgml-tools-1.0.0 and MAY NOT WORK WITH OLDER VERSIONS.
The installation is not automated but it is qute easy.
Create an empty directory and move there niceSgml2Html-0.4.tar.gz. Extract the contents with
gzip -dc niceSgml2Html-0.5.tar.gz | tar xv
Move the file niceHtml2Html.pm to <sgml-root>/SGMLTools
and fmt_html.pl to <sgml-root>/dist/ . You may need su
privileges to do this.
Move the file nicemapping to <sgml-root>/dist/linuxdoc/html
(where mapping is located).