Grouping By Ending Value (Code)
<xsl:for-each-group select="*"
group-ending-with="page[not(@continued
='yes')]">
<pageset>
<xsl:for-each select="current-group()">
<page><xsl:value-of select="."/></page>
</xsl:for-each>
</pageset>
</xsl:for-each-group>