Can you group in XSL?

Hi!

How could I group elements in XSL so a particular element is only displayed
once? I can retrieve all elements softed by category, but am not able to
surpress the repetitions.

For example, let's say I have the following XML and want the output to look
like this:

CATEGORY 1
     Title....description for this item
   subcategory
     Another title...description

CATEGORY 2
     Yet another title...Description



<?xml version="1.0" standalone="no"?> 
<glossary>
<glossaryitem>
	<category>Category 1</category>
	<english_title>Title</english_title>
	<english_description>Description for this item.
</english_description>
</glossaryitem>	
<glossaryitem>
	<category subcategory="Subcategory">Category 1</category>
	<english_title>Another title</english_title>
	<english_description>Description</english_description>
</glossaryitem>
<glossaryitem>
	<category>Category 2</category>
	<english_title>Yet Another title</english_title>
	<english_description>Description</english_description>
</glossaryitem>

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