Concatenating multiple input documents into a single node-set

Hi - 

I want to concatenate all of the nodes in a RELAX-NG schema (which is 
comprised of multiple included files) into a single node-set.  I've tried 
something like this:

<xsl:variable name="collection">
   <xsl:for-each select="//rng:include">
      <xsl:copy-of select="document(@href)" />
   </xsl:for-each>
</xsl:variable>

but I only get one node in the resulting variable.  Is there a better way to 
do this?


Thanks
Chris