Anne Ogborn's html tutorial

I am learning to use HTML generation via DCG as instructed in above.
My question is are all HTML tags define as nonterminal?  And is there one place, where there are documented?

For example:
phrase(
        html(html(
        [head(title('Howdy')),
         body([h1('A Simple Web Page'),
              p('With some text')])])),
        TokenizedHtml,
        []),
head, h1, must be defined , but I could not find them.  html_write documentation does not have p h1 etc>

Thanks Josef Frydl 
-------------- next part --------------
HTML attachment scrubbed and removed