XHTML output

Hi List,

I'm trying to get my output to be XHTML 1.0 Strict. We have a custom  
style sheet thus:

<xsl:import href="chunk-website.xsl" />
	
	<xsl:output encoding="utf-8"
				indent="no"
				method="xml"
				omit-xml-declaration="yes"
				doctype-public="-//W3C//DTD XHTML 1.0 Strict//EN"
				doctype-system="http://www.w3.org/TR/xhtml1/DTD/xhtml1- 
strict.dtd" />

but it does not  insert the DOCTYPE. Where do I change the output?

Many Thanks