function GWZ: real;
var k:real;
begin
  if m<5 then begin
    if g<0.65 then k:=1 else k:=0.71*g+0.54 end
  else
    if g<0.60 then k:=1 else
      if (g>=0.60) and (g<0.83) then k:=(0.52-0.017*m)*g+0.01*m+0.72 else
      k:=0.71*g+0.56-0.004*m;
  GWZ:=SQR(Tp-Tf)/(2*Tp*(1-g*Tf/Tp))*k;
end;