[1] W. Cheng, Z. W. Mo and J. Wang, Notes on the lower and upper approximations in a fuzzy
group and rough ideals in semigroups, Information Sciences, 177(22) (2007), 5134-5140.
[2] P. Corsini and V. Leoreanu, Applications of hyperstructure theory, Kluwer Academic Publishers,
Advances in Mathematics, 5 (2003).
[3] B. Davvaz, Roughness based on fuzzy ideals, Information Sciences, 176(16) (2006), 2417-
2437.
[4] B. Davvaz, Roughness in rings, Information Sciences , 164(1-4) (2004), 147-163.
[5] B. Davvaz, A new view of the approximations in Hv-groups, Soft Computing, 10 (2006),
1043-1046.
[6] B. Davvaz, Fuzzy Hv-groups, Fuzzy Sets and Systems, 101 (1999), 191-195.
[7] B. Davvaz and P. Corsini, Generalized fuzzy sub-hyperquasigroups of hyper- quasigroups, Soft
Computing, 10(11) (2006), 1109-1114.
[8] B. Davvaz and P. Corsini, Fuzzy n-ary hypergroups, J. of Intelligent and Fuzzy Systems,
18(4) (2007), 377-382.
[9] B. Davvaz and T. Vougiouklis, n-ary hypergroups, Iranian Journal of Science and Technology,
Transaction A, 30 (2006).
[10] W. D¨ornte, Untersuchungen auber einen verallgemeinerten gruppenbegri, Math. Z., 29
(1928), 1–19.
[11] D. Dubois and H. Prade, Rough fuzzy sets and fuzzy rough sets, Int. J. General Systems,
17(2-3) (1990), 191-209.
[12] V. G. Kaburlasos and V. V. Petridis, Fuzzy lattice neurocomputing (FLN) Models, Neural
Networks, 13 (2000), 1145-1170.
[13] N. Kuroki, Rough ideals in semigroups, Information Science , 100 (1997), 139-163.
[14] N. Kuroki and J. N. Mordeson, Structure of rough sets and rough groups, J. Fuzzy Math.,
5(1) (1997), 183-191.
[15] V. Leoreanu Fotea, The upper and lower approximations in a hypergroup, Information Sciences,
178 (2008), 3605-3615.
[16] V. Leoreanu Fotea, Several types of n-ary subhypergroup, Italian J. of Pure and Applied
Math., 23 (2008), 261-274.
[17] V. Leoreanu Fotea and B. Davvaz, Roughness in n-ary hypergroups, Information Sciences,
doi: 10.1016/j.ins.2008.06.019, 2008.
[18] V. Leoreanu Fotea and B. Davvaz, Join n-spaces and lattices, Multiple Valued Logic and Soft
Computing, accepted for publication in 15 (2008).
[19] V. Leoreanu Fotea and B. Davvaz, n-hypergroups and binary relations, European Journal of
Combinatorics, 29(5) (2008), 1207-1218.
[20] F. Marty, Sur une g´en´eralisation de la notion de group, 4th Congress Math. Scandinaves,
Stockholm (1934), 45-49.
[21] J. N. Mordeson and M. S. Malik, Fuzzy commutative algebra, Word Publ., 1998.
[22] S. Nanda and S. Majumdar, Fuzzy rough sets, Fuzzy Sets and Systems, 45 (1992), 157-160.
[23] Z. Pawlak, Rough Sets, Int. J. Comp. Inf. Sci., 11 (1982), 341-356.
[24] Z. Pawlak and A. Skowron, Rudiments of rough sets, Information Sciences, 177(1) (2007),
3-27.
[25] Z. Pawlak and A. Skowron, Rough sets: Some extensions, Information Sciences, 177(1)
(2007), 28-40.
[26] V. Petridis and V. G. Kaburlasos, Fuzzy lattice neural network (FLNN), A Hybrid Model for
Learning IEEE Transactions on Neural Networks, 9 (1998), 877-890.
[27] V. Petridis and V. G. Kaburlasos, Learning in the framework of fuzzy lattices, IEEE Transactions
on Fuzzy Systems, 7 (1999), 422-440.
[28] L. Polkowski and A. Skowron, Eds., Rough sets in knowledge discovery. 1. methodology and
applications. studies in fuzziness and soft computing, Physical-Verlag, Heidelberg, 18 (1998).
[29] L. Polkowski and A. Skowron, Eds., Rough sets in knowledge discovery. 2. applications.
studies in fuzziness and soft Computing, Physical-Verlag, Heidelberg, 19 (1998).
[30] A. Rosenfeld, Fuzzy groups, J. Math. Anal. Appl., 35 (1971), 512-517.
[31] M. M. Zahedi, M. Bolurian and A. Hasankhani, On polygroups and fuzzy subpolygroups, J.
Fuzzy Math., 3 (1995), 115.