[xsl] unparsed general entity in output !DOCTYPE

["Karjala Koponen" <kkoponen@xxxxxxxxxxxxxxxx>]

I need to create an unparsed general entity in the output xml DOCTYPE
'statement', as specified in our customer's (Elsevier)documentation:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE serial-issue PUBLIC "-//ES//DTD serials issue DTD version
5.1.0//EN//XML" "si510.dtd" [<!ENTITY cover SYSTEM "cover" NDATA IMAGE>]>


I'm thrashing here with things like:

<xsl:output method="xml" encoding="UTF-8" doctype-public="-//ES//DTD serials
issue DTD version 5.1.0//EN//XML" doctype-system='"si510.dtd" [&lt;!ENTITY
cover SYSTEM "cover" NDATA IMAGE&gt;]' indent="yes"/>

which gives me:

<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE serial-issue PUBLIC
"-//ES//DTD serials issue DTD version 5.1.0//EN//XML" ""si510.dtd" [<!ENTITY
cover SYSTEM "cover" NDATA IMAGE>]">
Note the extra quotes around ""si510.dtd" ... NDATA IMAGE>]".  If I remove the
single quotes I get an "Expected an attribute name" error.  I've tried many
variations with no better success.

I'm clearly searching for the answer incorrectly.  Mostly, I get "..not
generally used in practice." when I search on "unparsed general entity".

Where can I read about creating these 'heading' statements correctly?  And
what can I do to get my desired output?

Thanks, Karjala