[xsl] Know repeated values

[IZASKUN GUTIERREZ GUTIERREZ <igutierrez027@xxxxxxxxxxxxx>]

Hello everybody!

I have this template:

 <xsl:template match="/">

         <xsl:value-of select="file/entry/@id"/>

    </xsl:template>

I need know if in the result there are  repeated values and what they are.

Could anyvody help me?

thank you

Izaskun