theorem
  G is independent implies 'not' All(All(a,A,G),B,G) = Ex(Ex('not' a,B,G ),A,G)
proof
A1: Ex('not' a,B,G) = 'not' All(a,B,G) by BVFUNC_2:18;
  assume G is independent;
  hence thesis by A1,Th15;
end;
