Error: unknown value representation

Dear all,


This may be a new bee question, but after some google searching with no
solutions, I decided to ask on this list.

With the minimal example given below, I get the following error when processing
the file: unknown value representation. I working with docbook 4.4, xslt 1.69.0
and processed the file with Saxon8b.
The only thing I could find out myself was that the problem occurs only when I
insert the <bibliography>.  I'm using a separate bibliography file in which all
entries are stored. The stylesheet parameter bibliography.collection set to the
correct path.
This error did not occur when I was still working with docbook 4.3 and with an
earlier version of the xslt.

Could anybody tell me how to solve this problem?

Thanks!

Regards,
Robert.




<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN"
                         "http://www.docbook.org/xml/4.4/docbookx.dtd">
<article>
    <title>Article Title</title>
    <sect1>
        <title>Section1 Title</title>
        <para>The most important publication on this still is <biblioref
linkend="chomsky95"/>.</para>
    </sect1>
    <bibliography><title>Bibliography</title>
        <bibliomixed id="chomsky95"/>
    </bibliography>
</article>