Element type "xsl:stylesheet" must be declared

Hi all,
I need to declare some entities in my stylesheet.
Something like:

==================
<?xml version="1.0"?>
<!DOCTYPE xsl:stylesheet[ 
  <!ENTITY nbsp "&#160;">
]>

<xsl:stylesheet 
 xmlns:xsl="http://www.w3.org/1999/XSL/Transform"; 
 version="1.0">

..
</xsl:stylesheet>
==================

When the document is validated a got the error:

[Error] header.xsl:7:80: Element type "xsl:stylesheet" must be declared.

How can I declare entities in my stylesheet?!

Thank you very much,
Rui



-- 
Rui Alberto L. Gonçalves <rui-l-goncalves(_at_)ptinovacao(_dot_)pt>
PT Inovação


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