Multilevel Muenchian grouping -- Why doesn't this work

I want to group some entries first by year, and then by month.  My ideal
output is:

<h2>2003</h2>
 <h3>2</h3>
  <ul>...</ul>
 <h3>1</h3>
  <ul>...</ul>
<h2>2002</h2>
 <h3>12</h3>
  <ul>...</ul>
  ...

The XSLT I've come up with, with help from Jeni Tennison's site, is this
(relevant excerpt):

<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="html" doctype-public="-//W3C//DTD HTML 4.01//EN"/>
<xsl:key name="entry-year" match="entry" use="date/year"/>
xsl:key name="entry-month" match="entry" use="concat(date/year,
date/month)"/>

<xsl:for-each select="entry[count(. | key('entry-year', date/year)[1]) = 1]">
   <xsl:sort select="date/year" data-type="number" order="descending"/>

   <h2><xsl:value-of select="date/year"/></h2>

   <xsl:for-each select="key('entry-year', date/year)[count(. |
    key('entry-month', concat(date/year, date/month))[1]) = 1]">
     <xsl:sort select="date/month" data-type="number" order="descending"/>

     <h3><xsl:value-of select="date/month"/></h3>
     <ul>
         <xsl:for-each select="key('entry-month', concat(date/year,
         date/month))">
          [...]
         </xsl:for-each>
     </ul>
   </xsl:for-each>
</xsl:for-each>

The output this gets me on the input included below is:

<h2>2003</h2>
<h3>2</h3>
<ul></ul>
<h3>1</h3>
<ul></ul>
<h3>1</h3>
<ul></ul>
<h3>1</h3>
<ul></ul>
<h3>1</h3>
<ul></ul>
<h2>2002</h2>
<h3>11</h3>
<ul></ul>
<h3>11</h3>
<ul></ul>

I don't understand why all the months are showing up repeatedly, and
nothing inside at all.

The (relevant excerpt from the) input file looks like this:

<?xml version="1.0" encoding="UTF-8"?>
<booklog>
<entry id="159">
 <date>
  <year>2003</year>
  <month>2</month>
  <day>5</day>
 </date>
</entry>
<entry id="160">
 <date>
  <year>2003</year>
  <month>1</month>
  <day>9</day>
 </date>
</entry>
<entry id="161">
 <date>
  <year>2003</year>
  <month>1</month>
  <day>10</day>
 </date>
</entry>
<entry id="162">
 <date>
  <year>2003</year>
  <month>1</month>
  <day>11</day>
 </date>
</entry>
<entry id="163">
 <date>
  <year>2003</year>
  <month>1</month>
  <day>24</day>
 </date>
</entry>
<entry id="151">
 <date>
  <year>2002</year>
  <month>11</month>
  <day>12</day>
 </date>
</entry>
<entry id="150">
 <date>
  <year>2002</year>
  <month>11</month>
  <day>9</day>
 </date>
</entry>
</booklog>




-- 
Mike Kozlowski
http://www.klio.org/mlk/


 XSL-List info and archive:  http://www.mulberrytech.com/xsl/xsl-list