Re: alphabetic counters - Solved

For the archives, here is the final solution:

XML:
<food cite="bob1"/>
<food cite="bob2"/>
<food cite="jim"/>
<citation id="bob1" author="Bob et al." year="2004" title="Fish &amp; 
Chips" />
<citation id="bob2" author="Bob et al." year="2004" title="Bangers 
&amp; Mash" />
<citation id="jim" author="Jim et al." year="2004" title="Toad in the 
Hole" />
XSLT:
<xsl:key name="refs" match="citation" use="concat(@author,'+', @year)" 
/>
<xsl:for-each select="food">
  <xsl:value-of select="id(@cite)/@author" />
  <xsl:text> </xsl:text>
  <xsl:value-of select="id(@cite)/@year" />
  <xsl:variable name="cite" select="@cite" />
  <xsl:if test="count(key('refs', 
concat(id(@cite)/@author,'+',id(@cite)/@year))) &gt; 1">
    <xsl:for-each select="key('refs', 
concat(id(@cite)/@author,'+',id(@cite)/@year))">
      <xsl:if test="@id = $cite"><xsl:number value="position()" 
format="a" /></xsl:if>
    </xsl:for-each>
  </xsl:if>
</xsl:for-each>

Output:
Bob et al. 2004a
Bob et al. 2004b
Jim et al. 2003


Thanks to all who helped with this!
- Nick.