Link abstract to preface

Doc/lectures.xml

@@ -25,9 +25,8 @@
     </legalnotice>
 
     <abstract>
-      <para>Document is also available in <link
-      xlink:href="printversion.pdf">PDF</link> and <link
-      xlink:href="lectures.epub">Epub</link> format.</para>
+      <para>This Document is also available <link linkend="ava">other
+      formats</link>.</para>
 
       <para><mediaobject>
           <imageobject>

Doc/preface.xml

@@ -10,7 +10,7 @@
 
   <para>This document is available in the following formats:</para>
 
-  <glosslist>
+  <glosslist xml:id="availableFormats">
     <glossentry>
       <glossterm><uri
       xlink:href="https://freedocs.mi.hdm-stuttgart.de/webhelp">https://freedocs.mi.hdm-stuttgart.de/webhelp</uri></glossterm>