No Duplicate Contain() is Allowed?

XML:
     <bookshelf>
     <book>XSLT 2.0: From Beginning to Professional
       <topic>XML</topic>
      <publisher>Wiley</publisher></book>
     <book>XML in a Nutshell
     <publisher>Oreilly</publisher</book>
     <book>XSLT 2.0: Programmer's Reference
     <topic>XML</topic>
     <publisher>Wrox</publisher>
     </book>
     </bookshelf>

       <xsl:if test="contains(//book/*, 'XML')">
           <xsl:apply-templates/>
       </xsl:if>
      <xsl:if test="contains(//topic/*, 'XML')">
         <xsl:apply-templates/>
     </xsl:if>
</xsl:template>

Alice Wei
MIS 2008
School of Library and Information Science
Indiana University Bloomington