xml+xslt unique values Year

template.xslt

<xsl:if test="count(.//year) != 0">
    <div>
        <xsl:for-each select=".//year[generate-id() = generate-id(key('years',.)[1])]">
            <xsl:if test="./text() = /.//selected_year ">
                <xsl:attribute name="class">current</xsl:attribute>
            </xsl:if>
            <xsl:if test="position() = 1"></xsl:if><xsl:value-of select="." /> г.
        </xsl:for-each>
    </div>
</xsl:if>