diff --git a/Doc/Common/bibliography.xml b/Doc/Common/bibliography.xml
index 26a13aecd6c5c3e45129e1eac261a0c01f28eeaa..3bd50bc45262813c0a06313642ce6b9e12001db5 100644
--- a/Doc/Common/bibliography.xml
+++ b/Doc/Common/bibliography.xml
@@ -156,7 +156,8 @@
     <title>Harnessing Hibernate</title>
   </biblioentry>
 
-  <biblioentry xml:id="bib_fawcett2012">
+  <biblioentry xlink:href="http://proquest.safaribooksonline.com/book/web-development/xml/9781118239483"
+               xml:id="bib_fawcett2012">
     <abbrev>Fawcett2012</abbrev>
 
     <authorgroup>
@@ -430,7 +431,8 @@
     <title>Java ist auch eine Insel</title>
   </biblioentry>
 
-  <biblioentry xml:id="bib_Walmsley02">
+  <biblioentry xlink:href="http://proquest.safaribooksonline.com/book/web-development/xml/9780132886741"
+               xml:id="bib_Walmsley02">
     <abbrev>Walmsley2002</abbrev>
 
     <author>
diff --git a/Doc/Sda1/prerequisites.xml b/Doc/Sda1/prerequisites.xml
index 9ee79c2e0c149a9c5b8f1733a7d550cdcc5245d0..17fc93509b96840f5b21a5ba69ab39882945038f 100644
--- a/Doc/Sda1/prerequisites.xml
+++ b/Doc/Sda1/prerequisites.xml
@@ -19,11 +19,15 @@
         <glossdef>
           <itemizedlist>
             <listitem>
-              <para><xref linkend="bib_fawcett2012"/></para>
+              <para><xref linkend="bib_fawcett2012"/> possibly <link
+              xlink:href="http://proquest.safaribooksonline.com/book/web-development/xml/9781118239483">accessible
+              online</link>.</para>
             </listitem>
 
             <listitem>
-              <para><xref linkend="bib_Walmsley02"/></para>
+              <para><xref linkend="bib_Walmsley02"/> possibly <link
+              xlink:href="http://proquest.safaribooksonline.com/book/web-development/xml/9780132886741">accessible
+              online</link>.</para>
             </listitem>
           </itemizedlist>
         </glossdef>