diff --git a/xsl/caramel/concept2docbook.xsl b/xsl/caramel/concept2docbook.xsl
index 29428eb..21585dc 100644
--- a/xsl/caramel/concept2docbook.xsl
+++ b/xsl/caramel/concept2docbook.xsl
@@ -759,7 +759,7 @@ top level of the Caramel distribution. -->
 
   <xsl:template name="concept.link">
     <xsl:param name="name" select="text()"/>
-    <xsl:param name="warn" select="true"/>
+    <xsl:param name="warn" select="true()"/>
     <xsl:param name="text" select="$name"/>
     <xsl:variable name="node" select="key('concepts', $name)"/>
     
@@ -767,7 +767,7 @@ top level of the Caramel distribution. -->
       <xsl:when test="count($node)=0">
         <xsl:if test="$warn">
           <xsl:message>
-            <xsl:text>Cannot find concept '</xsl:text>
+            <xsl:text>warning: cannot find concept '</xsl:text>
             <xsl:value-of select="$name"/>
             <xsl:text>'</xsl:text>
           </xsl:message>
diff --git a/xsl/docbook.xsl b/xsl/docbook.xsl
index 2f3afb6..8bc369a 100644
--- a/xsl/docbook.xsl
+++ b/xsl/docbook.xsl
@@ -42,6 +42,33 @@
               <xsl:text>Reference</xsl:text>
             </title>    
           </xsl:if>
+
+          <xsl:if test="concept">
+            <section>
+              <title>Concepts</title>
+
+              <xsl:if test="ancestor::library/attribute::id">
+                <xsl:attribute name="id">
+                  <xsl:value-of select="ancestor::library/attribute::id"/>
+                  <xsl:text>.concepts</xsl:text>
+                </xsl:attribute>
+              </xsl:if>
+
+              <itemizedlist>
+                <xsl:for-each select="concept">
+                  <listitem>
+                    <xsl:call-template name="internal-link">
+                      <xsl:with-param name="to">
+                        <xsl:call-template name="generate.id"/>
+                      </xsl:with-param>
+                      <xsl:with-param name="text" select="@name"/>
+                    </xsl:call-template>
+                  </listitem>
+                </xsl:for-each>
+              </itemizedlist>
+            </section>
+          </xsl:if>
+
           <xsl:apply-templates/>
         </section>
       </xsl:otherwise>