Problem with obtaining distinct values from a variable

I have a nagging problem with a nodeset variable. I have a parameter
"$services" that I iterate through. This is a nodeset that I pass into
the stylesheet.

I can have repetitive values in this nodeset and want to remedy this
situation. I have tried using sibling elemination and couldn't see a way
to apply grouping. I am always getting an invalid xpath error.

How would I go about getting distinct values from the single parameter
"$services"?

Ian 

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