variable question

Is there some obvious reason why the "title-before" variable below  
doesn't work when called from within a template?
I'm not sure if the problem is that there's something wrong with the  
way I'm trying to use variables, or something about the context and the  
xpath expressions (my guess is the latter).
Bruce

<xsl:variable name="reftype">
  <xsl:choose>
    <xsl:when test="not[mods:relatedItem[(_at_)type='host']]">
      <xsl:text>book</xsl:text>
    </xsl:when>
    <xsl:when
      
test="mods:relatedItem[(_at_)type='host']/mods:originInfo/mods: 
issuance='continuing'">
      <xsl:text>article</xsl:text>
    </xsl:when>
    <xsl:when
      
test="mods:relatedItem[(_at_)type='host']/mods:originInfo/mods: 
issuance='monographic'">
      <xsl:text>chapter</xsl:text>
    </xsl:when>
  </xsl:choose>
</xsl:variable>

<xsl:variable name="title-before">
  <xsl:choose>
    <xsl:when test="$reftype='chapter'">
      <xsl:text>“</xsl:text>
    </xsl:when>
    <xsl:otherwise>
      <xsl:text></xsl:text>
    </xsl:otherwise>
  </xsl:choose>
</xsl:variable>