<p name='eps'>
  <p name='NAZN'>
    <p name='SUM_1'>1.11 </p> 
    <p name='SUM_13'>1.11 </p> 
    <p name='SUM_147'>1.11 </p> 
  </p>
</p>

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    <xsl:output method="xml" version="1.0" encoding="utf-8" omit-xml-declaration="yes" indent="yes"/>
    <xsl:template match="/">
        <root>
            <xsl:value-of select="sum(//p[@name='eps']/p[@name='NAZN']/p[contains(@name,'SUM_')])"/>
        </root>
    </xsl:template>
</xsl:stylesheet>