compilation error porting gnans ?

[Balbir Thomas <thomas.1037@osu.edu>]

Hi,
I am trying to compile the GNU program gnans (unfortunately unmaintained now ) 
on sid . It used to compile well on potato . But now I get error messages as :

./gnanslib/.libs/libgnanslib.so -lfl -lg++ -lstdc++ -ldl -lXext -lXmu -lXt -lX11 -lSM -lICE -ltermcap -lf2c -lm -Wl,-rpath -Wl,/usr/X11R6/lib -Wl,-rpath -Wl,/usr/lib/gcc-lib/i386-linux/2.95.4
Plotter.o: In function `Plotter::Plotter(_WidgetRec *, PlotterControl const *)':/home/bt/bin/gnans/src/Plotter.cc:210: undefined reference to `formWidgetClass'
/home/bt/bin/gnans/src/Plotter.cc:217: undefined reference to `menuButtonWidgetClass'
/home/bt/bin/gnans/src/Plotter.cc:218: undefined reference to `simpleMenuWidgetClass'
--More--(24%

Could you please tell me which library provides formWidgetClass e.t.c. And 
in general how does one findout which library provides a particular function.

Thanking you
B.Thomas