<?xml version='1.0' encoding='utf-8'?>
<xsl:stylesheet version='1.0' xmlns:xsl='http://www.w3.org/1999/XSL/Transform'>

  <!-- Copy tree with holding its structure -->
  <xsl:template match="@*|node()" priority="-1">
    <xsl:copy><xsl:apply-templates select="@*|node()"/></xsl:copy>
  </xsl:template>
 
  <xsl:template match="@*|node()" mode="xhtml">
    <xsl:copy><xsl:apply-templates select="@*|node()"/></xsl:copy>
  </xsl:template>

</xsl:stylesheet>