parameters in xsp don't work

I must create an dynamic variable based (from db content) cinclude path.
But this doens't work. Do you know why?
...
<esql:results>
<esql:row-results>
     <xsl:variable name="id"><esql:get-string column="i.id"/></xsl:variable>
    <xsl:variable name="stylesheet-path"><esql:get-string
column="t.stylesheet"/></xsl:variable>
    <cinclude:include
src="cocoon://rauser-cocoon/abstract_{$id}_styleWith_{$stylesheet-path}"/>
</esql:row-results>
</esql:results>
....


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