b c a x1 a b x1 b b b x1 c a c x1 c d x1 d c x1 c d b x1 d c c x1 d c x1 b b b x1 c b x1 d a x1 d b c x1 a a x1 d a x1 b x1 b 1 c 1 a 1 d 1 FULL ./SRS/Zantema/z081.srs