sub4, sub6 :: LNSubstVFresh
sub4 = substFromListVFresh [(lx1, x4), (lx2, x4)]
sub4, sub6 :: LNSubstVFresh
sub4 = substFromListVFresh [(lx1, x4), (lx2, x4)]
sub4 = substFromListVFresh [(lx1, x4), (lx2, x4)]