Re: use-when attribute?

However, I'm not sure whether this is the right design for your problem. I
would be inclined to stick with the traditional approach: the
special-purpose stylesheet module (here, the XHTML output module) should
import the general-purpose module, not the other way around; and you then
decide which special-purpose module to use by using that as your entry point
to the transformation.

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
  xmlns:db="http://docbook.org/docbook-ng" version="2.0">
  <xsl:variable name="citerefs" select="//db:biblioref/@linkend"/>
</xsl:stylesheet>