Mixing imports and includes - specified behaviour?

Hi there,

in this example I found different result from different XSLT processors,
just call main.xsl with input '<one/>':

main.xsl :
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform" >
<xsl:include href="first.xsl"/>
<xsl:include href="second.xsl"/>
<xsl:template match="/">
  <b>
   <xsl:for-each select="one | two | three | four">
  <xsl:apply-templates select="."/>
  </xsl:for-each>
  </b>
</xsl:template>
</xsl:stylesheet>

first.xsl :
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform" >
<xsl:template match="one">
  <xsl:apply-imports/>
  <xsl:text>1</xsl:text>
</xsl:template>
<xsl:template match="two">
  <xsl:text>2</xsl:text>
</xsl:template>
</xsl:stylesheet>

second.xsl :
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform" >
<xsl:import href="third.xsl"/>
<xsl:template match="three">
  <xsl:text>3</xsl:text>
</xsl:template>
<xsl:template match="four">
  <xsl:text>4</xsl:text>
</xsl:template>
</xsl:stylesheet>

third.xsl :
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform" >
<xsl:template match="one">
  <xsl:text>this is also one</xsl:text>
</xsl:template>
</xsl:stylesheet>

And this is how it works: In main.xsl I include two stylesheets. In one
stylesheet I import a template that is activated in the other.

I have following question: Is the result defined in XSLT 1.0 and XSLT 2.0?

Thanks in advance 
Tobias