[xsl] grouping data

Hi there,

Need some help here...

I'm trying to group data using XSLT. I've read that this can be done by
building a unique lis, but I do not succeed in buiding this unique list. Can
someone help me out here?

Thanks.
Marco

XML:
<response>
	<elem>
		<groupname>grp1</groupname>
		<groupvalue>foo</groupvalue>
		.......
	</elem>
	<elem>
		<groupname>grp2</groupname>
		<groupvalue>foo</groupvalue>
		.......
	</elem>
	<elem>
		<groupname>grp1</groupname>
		<groupvalue>foo</groupvalue>
		.......
	</elem>
</response>




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