LinuxDoc

LinuxDoc is both a collection of utilities and a file format based on SGML. It is basically a clone of the SGML version of DocBook with some variations and its use is mostly confined to the Linux world, and its use appears to have faded significantly in the last decade.

Text editors with LinuxDoc support

 * FTE - Has support for syntax highlighting, code folding and syntax-aware auto-indent.

Links

 * Creating documentation with LinuxDoc - from Debian.org