Saxon Quirk

I posted this on the Saxon list yesterday, but then I started to think that
there might be a better way to generate the list that I wanted. Any thoughts
would be greatly appreciated.

Regards,
Kurt
---
I've been using Instant Saxon 6.2 to try to generate a list based on two
attributes of a tag as given by the allpubs variable below. I've been
questioning the validity of my XSL, but I get the expected output in MSXML3
and Xalan2.0.0 (although Xalan1.0.2 was broken). 

<!-- allpubs.xsl -->
<xsl:stylesheet version="1.1"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:variable name="allpubs"
select="//pubtag[@list='yes']/@pub[not(.=preceding::pubtag[@list='yes']/@pub
)]" />
<xsl:template match="/">
	<xsl:for-each select="$allpubs">
		<xsl:value-of select="." /><br />
	</xsl:for-each>
</xsl:template>
</xsl:stylesheet>

<!-- allpubs.xml -->
<?xml version="1.0"?>
<?xml-stylesheet type="text/xsl" href="allpubs.xsl"?>
<publist>
	<pubtag list='yes' pub='xml journal' />
	<pubtag list='no'  pub='fortran journal' />
	<pubtag list='yes' pub='xml journal' />
	<pubtag list='yes' pub='xsl journal' />
	<pubtag list='yes' pub='css journal' />
	<pubtag list='yes' pub='xml journal' />
	<pubtag list='no'  pub='cobol journal' />
	<pubtag list='no'  pub='ada journal' />
	<pubtag list='no'  pub='fortran journal' />
	<pubtag list='no'  pub='snobol journal' />
	<pubtag list='yes' pub='xsl journal' />
</publist>

<!-- Expected Output -->
xml journal
xsl journal
css journal

<!-- Instant Saxon 6.2 Output -->
xml journal
xml journal
xsl journal
css journal
xml journal
xsl journal


 XSL-List info and archive:  http://www.mulberrytech.com/xsl/xsl-list