Selecting multi-existant elements only once

Hi all,

I've got a XML-File with following structure. There are different 
departements and in each departement there are different professions. I 
want to have every profession of all departement once... If there is a 
Manager in departement a and departement b, "Manager" should only be 
printed out once...
How can I do that?

[...]
<departement>
 <profession>
   <desc>Manager</desc>
   <salary>5000</salary>
 </profession>

 <profession>
   <desc>Assistant</desc>
   <salary>3000</salary>
 </profession>

 <profession>
   <desc>Employee</desc>
   <salary>2000</salary>
 </profession>
</departement>

<departement>
 <profession>
   <desc>Manager</desc>
   <salary>5000</salary>
 </profession>

 <profession>
   <desc>Worker</desc>
   <salary>2000</salary>
 </profession>
</departement>

[...]

Thanks for your help !

Sorin


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