DOCBOOK: Processing article

[Fredrik Eriksson <fredrik.eriksson@flowsystems.se>]

I am newbie and trying to understand this docbook stuff. An from the
www.docbook.org I took an example of a document as you can see below and
trying to process it with openjade with no luck. I run this :

openjade -t sgml -E 2 -d $SGML_SHARE/dsssl/html/docbook.dsl article.xml

And all I get out is :

openjade:/usr/local/share/docbook/xml/docbookx.dtd:74:17:E: "X20AC" is not a
function name
openjade:/usr/local/share/docbook/xml/ent/iso-amsa.ent:8:19:E: "X21B6" is
not a function name
openjade:/usr/local/share/docbook/xml/ent/iso-amsa.ent:9:19:E: "X21B7" is
not a function name

What have I done worng and what do I need to process the example below?
<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
          "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd">
<article>
<articleinfo>
  <author><firstname>Norman</firstname><surname>Walsh</surname></author>
  <authorinitials>ndw</authorinitials>
  <artpagenums>339-343</artpagenums>
  <volumenum>15</volumenum>
  <issuenum>3</issuenum>
  <publisher><publishername>The TeX User's Group</publishername></publisher>
  <pubdate>1994</pubdate>
  <title>A World Wide Web Interface to CTAN</title>
  <titleabbrev>CTAN-Web</titleabbrev>
  <revhistory>
     <revision>
        <revnumber>1.0</revnumber>
        <date>28 Mar 1994</date>
        <revremark>Submitted.</revremark>
     </revision>
     <revision>
        <revnumber>0.5</revnumber>
        <date>15 Feb 1994</date>
        <revremark>First draft for review.</revremark>
     </revision>
  </revhistory>
</articleinfo>
<para>
The body of the article &hellip;
</para>
</article>