How can repitition be avoided in XSL

How can repitition be avoided with xsl for the example input xml and  output 
html file given below:
Input XML
<Parent>
 <Class>
   <Parameter>
     <Name>P1</Name>
     <Type>str</Type>
   </Parameter>
   <Parameter>
     <Name>P2</Name>
     <Type>int</Type>
   </Parameter>
   <Parameter>
     <Name>P3</Name>
     <Type>str</Type>
   </Parameter>
   <Parameter>
     <Name>P4</Name>
     <Type>str</Type>
   </Parameter>
 </Class>
 <Class>
   <Parameter>
     <Name>P5</Name>
     <Type>str</Type>
   </Parameter>
   <Parameter>
     <Name>P1</Name>
     <Type>str</Type>
   </Parameter>
   <Parameter>
     <Name>P6</Name>
     <Type>str</Type>
   </Parameter>
 </Class>
</Parent>

output HTML
Parameters are:
P1
P2
P3
P4
P5
P6

 Thank you.
   Raghava



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