DocBook 5.0 DTD public identifier?

["Bob Stayton" <bobs@sagehill.net>]

Hi,
For those who must use the DTD version of DocBook 5.0 because of the 
limitations of their tools, what are the PUBLIC and SYSTEM identifiers that 
should be used, if one wanted their DOCTYPE to resemble that of DocBook 4.5:

<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
                    "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd";>

I can't find the public identifier information in the spec or in the schema 
distribution.

Regarding the system identifier, there is nothing at this URL:

http://www.oasis-open.org/docbook/xml/5.0/dtd/docbook.dtd

Shouldn't there be?  There is for 5.0b5.

Bob Stayton
Sagehill Enterprises
bobs@sagehill.net