Does anyone know how to write this anchor tag?

<!--This template formats various head (here, series unittitles) elements and makes them targets for links from the Table of Contents.-->

<xsl:template match="c01[@level='series']/did/unittitle">
            <a name="?">  

<!--The path needs to read ($file)b.html#series + position(), for example:filenameb.html#series2, see href established in TOC pasted below. -->


<!-- Displays the unittitle and unitdates for a c01 if it is a series (as
evidenced by the level attribute series)and numbers them
to form a hyperlink to each. -->

<xsl:for-each select="archdesc/dsc/c01[@level='series' or @level='subseries'
            or @level='subgrp' or @level='subcollection']">
                <p style="margin-left:10pt; font-size:10pt">
                        <xsl:attribute name="href">
                            <xsl:value-of select="$file"/>b.html#series<xsl:number value="position()" format="1"/>

Thanks you,