function xdot=GFNfun(t,x);
% Carol Lucas
% Called function for Gfitz_Nag.m
% Note that all parameters are set in the calling program

global Af betaf deltaf Cf epsf gamf tend vinitf winitf

V=x(1);
W=x(2);
xdot(1,1)=Af*V*(V-betaf)*(deltaf-V)-Cf*W;
xdot(2,1)=epsf*(V-gamf*W);