title: how to check duplicate element values using xslt
body: <pre><code>    &lt;BookList&gt;
      &lt;Book&gt;
      &lt;History&gt;
      &lt;Type&gt;history&lt;/Type&gt;
      &lt;Prize&gt;123&lt;/Prize&gt;
      &lt;Publication&gt;``
      &lt;Name&gt;YEAP1&lt;/Name&gt;
      &lt;/Publication&gt;
      &lt;RNumber Type="VolumeNumber"&gt;11111&lt;/RNumber&gt;
      &lt;RNumber Type="SupplementNumber"&gt;123456&lt;/RNumber&gt;
      &lt;/History&gt;
      &lt;chemistry&gt;
      &lt;Type&gt;chemistry&lt;/Type&gt;
      &lt;Prize&gt;333&lt;/Prize&gt;
      &lt;Publication&gt;
      &lt;Name&gt;YEAP&lt;/Name&gt;
      &lt;/Publication&gt;
      &lt;RNumber Type="VolumeNumber"&gt;11111&lt;/RNumber&gt;
      &lt;RNumber Type="SupplementNumber"&gt;45454&lt;/RNumber&gt;
      &lt;/chemistry&gt;
                        ......
  
      &lt;/Book&gt;
      &lt;/BookList&gt;
  </code></pre>
  
  <p>There are duplicate VolumnNumber 11111. How to check duplicate VolumnNumber in BoolList xml using xslt . please help on this</p>