Remove DOCTYPE from XML document generated from Docbook?

[Matej Cepl <mcepl@redhat.com>]

Hi,

trying to produce ATOM feed from a Docbook (customized) only with 
XSLT. The problem is that even though my <xsl:output> looks like 
(the complete XSL stylesheet is at 
http://mcepl.fedorapeople.org/tmp/atom.xsl):

<xsl:output
  indent="yes"
  encoding="utf-8"/>

xsltproc still generates HTML DOCTYPE and xmlns:

<?xml version="1.0" encoding="utf-8" standalone="yes"?>
<!DOCTYPE atom:feed PUBLIC "-//W3C//DTD XHTML 1.0 
    Transitional//EN" 
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd";>
<atom:feed xmlns:atom="http://purl.org/atom/ns#"; 
xmlns:date="http://exslt.org/dates-and-times"; 
xmlns:dc="http://purl.org/dc/elements/1.1/"; xml:lang="en" 
lang="en">
 
How to avoid elimination of doctype-public and doctype-system as 
they are apparently imported from the xhtml/docbook.xsl? (of 
course, I know that there is no public DOCTYPE for atom).

Best,

Matěj Cepl