I implemented the definition of the SGML converter for reasons of backward
compatibility at our site (the ICCE). The SGML converter is by no means
complete, or indeed usable unless you're using the SGML system at the ICCE. It
outputs an SGML file which is suitable for bf(our) SGML implementation, which
is a hacked Linuxdoc-SGML mutant.

For these reasons, the SGML converter only supports the tt(article) document 
type. Therefore, the top-level sectioning command can only be tt(sect). 

The SGML converter adds two macros to the set: tt(sgmltag(tag)(onoff)) and
tt(sgmlcommand(cmd)), which work similarly to the tt(htmltag) and 
tt(htmlcommand) macros. 
