This document type declaration refers to the level 1 HTML DTD with the `HTML.Recommended' entity defined as `INCLUDE' rather than IGNORE; that is, it refers to the more structurally rigid definition of HTML.
<!-- html-1s.dtd
Document Type Definition for the HyperText Markup Language
Struct Level 1
$Id: 96.htm,v 1.1.1.1 1998/09/05 02:18:12 baccala Exp $
Author: Daniel W. Connolly <connolly@w3.org>
See Also: http://www.w3.org/hypertext/WWW/MarkUp/MarkUp.html
-->
<!ENTITY % HTML.Version
"-//IETF//DTD HTML 2.0 Strict Level 1//EN"
-- Typical usage:
<!DOCTYPE HTML PUBLIC
"-//IETF//DTD HTML Strict Level 1//EN">
<html>
...
</html>
--
>
<!-- Feature Test Entities -->
<!ENTITY % HTML.Recommended "INCLUDE">
<!ENTITY % html-1 PUBLIC "-//IETF//DTD HTML 2.0 Level 1//EN">
%html-1;