DOCBOOK: : in docbook -> html

Hi

I'm using Norm'S stylesheets to convert docbook into html
documentation (and ps).  Thereby I discovered that entitiy references
to : (from ison-num.gml) are expanded into : again.

I'd like to change that to yield a literal ":"

But I don't want to break the postscript output, which is correct, nor
do I want to change every document ever written.

The question is: is there a resonable place, where to adapt the
docbook dtd?  Is this feasible at all?

Thanks for any help

/Jerry

-- 
The worst of harm may often result from the best of intentions.