The HTML 2.0 Proposed Standard, RFC 1866, is a product of the HTML Working Group of the IETF, edited by Dan Connolly.
Network Working Group T. Berners-Lee Request for Comments: 1866 MIT/W3C Category: Standards Track D. Connolly November 1995
The published RFC is the same in content as the September 22 draft, which is available here in several formats:
For folks that want to play around with the SGML source: It uses a document type by Gary Houston called Snafu. His GF: General SGML Formatter package includes this DTD and a few others, and some nifty tools to build TeXinfo, RTF, etc. from SGML documents.