Problem with MathML entities in PDF

[Giulio Piancastelli <gpian@softhome.net>]

Hi all,

I'm trying to use some of MathML entities in my DocBook files. I managed 
to have aliases for such entities recognized by using the following 
DOCTYPE declaration:

<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook V4.3//EN" 
"file:///C:/Programmi/Xml/DTDs/docbook43/docbookx.dtd" [

   <!ENTITY % ent-mmlalias PUBLIC "-//W3C//ENTITIES Aliases for MathML 
2.0//EN" "C:/Java/Xml/DTDs/mathml2/mathml/mmlalias.ent" >
     %ent-mmlalias;
]>

but, when I try to transform the DocBook + MathML entities markup to 
XSL-FO then to PDF I keep seeing other symbols (i.e. '#') in places 
where "fancy" MathML symbols should appear (e.g. the &Intersection; 
symbol, the &emptyset; symbol). Has this something to do with fontsets 
used by FOP, which seem to be unable to recognize and display certain 
unicode characters? Is there a workaround so that I can obtain 
mathematical symbols in PDF output format? (When using XHTML as the 
output format, everything works like a charm.)

Best Regards,
Giulio Piancastelli.