<xsl:choose>
<xsl:when test="string-length(fields/title) > 0"><xsl:value-of select="fields/title"/></xsl:when>
<xsl:when test="string-length(fields/htmltitle) > 0"><xsl:value-of select="fields/htmltitle"/></xsl:when>
<xsl:when test="string-length(title) > 0"><xsl:value-of select="title"/></xsl:when>
<xsl:otherwise>Untitled</xsl:otherwise>
</xsl:choose>
_.html