docbook v3.1

To Whoever This Concerns,

I have downloaded SGML Version 3.1 of DocBook. I am compiling it in
Softquad Author/Editor using Rulesbuilder. The compiling works without
any problems but when I try to use compiled version I get the message

Error in Document Type Declaration in the document: Character is of the
wrong type. 
"'" (34) is not a minimum data character.

I get this message when I compile on the PC and also on UNIX. Can
someone point out the problem so I can fix it.

I have used the Declaration that was supplied in the ZIP archive for
Version 3.1

Your help is greatly appreciated.

Denny Miller
SGML/XML Specialist
PRDGROUP Inc.
210-234 York Street
York, PA  17403