complicacy of sorting

Hello.

I write this:

<xsl:for-each select="CountryList/Country">
<xsl:sort order="ascending" 
select="//MonthPriceCountryList/MonthPriceCountry[(_at_)CountryID=current()/@ID][
@IStationID=$isid]/@Price"/>
        <xsl:if test="position()=1">
                <xsl:value-of 
select="//MonthPriceCountryList/MonthPriceCountry[(_at_)CountryID=current()/@ID][
@IStationID=$isid]/@Price"/>
        </xsl:if>
</xsl:for-each>

I need to get minimum Price from all Country (from CountryList).
Each Country has attribute ID, and each MonthPriceCountry has attribute 
CountryID, which are the same values.
For some reason sorting doesn't implements. 
Please, please, help me to find out the mistake.


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