display parts of XML tree with xsl:copy ?

How can I solve the following problem?

>From the following article DB (SigmodRecord) i want to e.g. only articles by
a certain author
but the result tree should still contain the information of <number> which
is nearer to the root.

Below you also find my test query.

######################### SAMPLE XML
###############################################

<issue>
 <volume>11</volume>
 <number>1</number>
 <articles>
  <article>
   <title>Annotated Bibliography on Data Design.</title>
   <initPage>45</initPage>
   <endPage>77</endPage>
   <authors>
    <author position="00">Anthony I. Wasserman</author>
    <author position="01">Karen Botnich</author>
   </authors>
  </article>

  <article>
   <title>Architecture of Future Data Base Systems.</title>
   <initPage>30</initPage>
   <endPage>44</endPage>
   <authors>
    <author position="00">Lawrence A. Rowe</author>
    <author position="01">Michael Stonebraker</author>
   </authors>
  </article>
  <!-- a lot more articles //-->
 </articles>
  </issue>
  <issue>
   <volume>11</volume>
   <number>2</number>
   <articles>

  <!-- a lot more articles //-->

################### MY XSLT - QUERY
##########################################

<?xml version="1.0"?>
<xsl:transform version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="xml"/>

 <xsl:template match="/child::*">
   <xsl:copy>
     <xsl:for-each select="//article">
    <xsl:choose>
   <xsl:when test=".//author='Karen Botnich'">
     <xsl:copy-of select="."/>
   </xsl:when>

   <xsl:otherwise/>
    </xsl:choose>
  </xsl:for-each>
   </xsl:copy>
 </xsl:template>

</xsl:transform>

If I use <xsl:copy-of select=".."/> instead of <xsl:copy-of select="."/> I
get even those <articles> that
don't fullfil my query, but I only want the issue-number.


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