Add rend="URN" attribute to idno elements of type URN
see #24
diff --git a/xslt/epub2i5.xsl b/xslt/epub2i5.xsl
index 2c59831..734e644 100644
--- a/xslt/epub2i5.xsl
+++ b/xslt/epub2i5.xsl
@@ -333,6 +333,9 @@
<idno type="{$type}"><xsl:value-of select="replace(., '(([0-9]|-)+X?).*', '$1')"/></idno>
</xsl:if>
</xsl:when>
+ <xsl:when test="$type='URN'">
+ <idno rend="URN" type="URN"><xsl:value-of select="."/></idno>
+ </xsl:when>
<xsl:otherwise><idno type="{$type}"><xsl:value-of select="."/></idno></xsl:otherwise>
</xsl:choose>
</xsl:for-each>