HTX recognises a cross-reference target with the form:
<A NAME="xref_">any text</A>
(i.e. with a blank label) as a special case, to be used to identify the ``top'' page of a hypertext document. This should be the point to which a reader is transferred if the entire document is requested and no particular part of it is specified.
Any other document can refer to this label, using an anchor with the form:
<A HREF="/any_where/docname.htx/any_file.html#xref_">any text</A>
but its inclusion as a cross-reference target in the referenced document is optional. If it is omitted, HTX will assume that the top HTML page in a document is named after the document itself. That is, it will use a URL such as:
/some_where/docname.htx/docname.html#xref_
If your document does not follow this convention, then you should include a cross-reference target with a blank label at the start of whichever HTML file serves the same purpose.