When pre-compiling KDE docs for use in an XFCE desktop, I found this error:

    root@heavy:/# yelp-build html --path /usr/share/kf6/kdoctools/customization/dtd /usr/share/doc/HTML/et/kioworker6/ldap/index.docbook
    /usr/share/doc/HTML/et/kioworker6/ldap/index.docbook:7: warning: failed to load external entity "/usr/share/doc/HTML/et/kioworker6/ldap/dtd/kdebx45.dtd"
    ]>
      ^
    /usr/share/doc/HTML/et/kioworker6/ldap/index.docbook:9: parser error : Entity 'language' not defined
    <article lang="&language;" id="ldap">
                             ^
    /usr/share/doc/HTML/et/kioworker6/ldap/index.docbook:15: parser error : Entity 'Lauri.Watts' not defined
    >&Lauri.Watts; &Lauri.Watts.mail;</author>
                  ^
    /usr/share/doc/HTML/et/kioworker6/ldap/index.docbook:15: parser error : Entity 'Lauri.Watts.mail' not defined
    >&Lauri.Watts; &Lauri.Watts.mail;</author>

Comparing this file to other files, I think this is a simple typo.

    root@heavy:/# grep -h 45.dtd /usr/share/doc/HTML/*/kioworker6/ldap/index.docbook | sort | uniq -c
          1 "dtd/kdebx45.dtd" [
         18 "dtd/kdedbx45.dtd" [

I think this is the appropriate fix:

     <?xml version="1.0" ?>
     <!DOCTYPE article PUBLIC "-//KDE//DTD DocBook XML V4.5-Based Variant V1.1//EN"
    -"dtd/kdebx45.dtd" [
    +"dtd/kdedbx45.dtd" [
     <!ENTITY % addindex "IGNORE">
     <!ENTITY % Estonian  "INCLUDE"