isotech entities not rendered

["A.R. (Tom) Peters" <tpeters@xs4all.nl>]

I'd like to use 2 entities from %isotech;: ≠ (not-equals sign) and
− (a minus sign).  I use MATHML:
<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.0//EN"
 "http://www.oasis-open.org/docbook/xml/mathml/1.0/dbmathml.dtd";
[ ... ]>

However, both are rendered with a hash '#'.  What do I need to do to get
the proper glyphs?
I work on Debian, and use xlstproc and fop to generate printable output.

	Thanx,
--
#>!$!%(@^%#%*(&(#@#*$^@^$##*#@&(%)@**$!(&!^(#((#&%!)%*@)(&$($$%(@#)&*!^$)^@*^@)

	Tom Peters