why is the HTML4 reference normative?

The only reference I can find to HTML4 in the text
is "the <script> element allows the specification of a block of
client-side scripting language code, and is analogous to the [HTML4]
<SCRIPT> element."
 -- http://www.w3.org/TR/2004/WD-voicexml21-20040728/#sec-script_expr

That looks informative, to me.

Why is HTML4 listed among the normative references?

-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/