+class MathData;
+
+void write(MathData const &, WriteStream &);
+void htmlize(MathData const &, HtmlStream &);
+void normalize(MathData const &, NormalStream &);
+void maple(MathData const &, MapleStream &);
+void maxima(MathData const &, MaximaStream &);
+void mathematica(MathData const &, MathematicaStream &);
+void mathmlize(MathData const &, MathStream &);
+void octave(MathData const &, OctaveStream &);