How about something like:
<!ENTITY that CDATA "þæt">
Assuming this is legal, does/will "Arena" support this?
--- Tony Jebson --- International Computers Limited (ICL)
--- firstname.lastname@example.org --- http://www.to.icl.fi/~aj/index.html
--- All opinions expressed here (however stupid) are my own,
--- and nothing stated here is an official statement by ICL.