JPA collection links added

Doc/Sda1/jpaintro.xml

@@ -348,8 +348,12 @@ TRACE [main] sql.BasicBinder (BasicBinder.java:65) - binding parameter [1] as [V
                 <tip>
                   <para>Since <classname>Description</classname> instances are
                   composites with respect to <classname>Product</classname>
-                  you might want to use @ElementCollection in favour of
-                  @ManyToOne / @OneToMany.</para>
+                  you might want to use <interfacename
+                  xlink:href="https://en.wikibooks.org/wiki/Java_Persistence/ElementCollection">@ElementCollection</interfacename>
+                  in favour of <interfacename
+                  xlink:href="https://en.wikibooks.org/wiki/Java_Persistence/ManyToOne">@ManyToOne</interfacename>
+                  / <interfacename
+                  xlink:href="https://en.wikibooks.org/wiki/Java_Persistence/OneToMany">@OneToMany</interfacename>.</para>
                 </tip>
 
                 <para>Test your implementation by uncommenting the test