[1] P. S. Das, Fuzzy groups and level subgroups, J. Math. Anal. Appl., 84 (1981), 264-269.
[2] Y. I. Kwon and S. K. Lee, The weakly semi-prime ideals of po−$\Gamma$−semigroups, Kangweon-
Kyungki Math. J., 5 (1997), 135-139.
[3] Y. I. Kwon and S. K. Lee, On the left regular po−$\Gamma$−semigroups, Kangweon-Kyungki Math.
J., 6 (1998), 149-154.
[4] W. J. Liu, Fuzzy invariant subgroups and fuzzy ideals, Fuzzy Sets and Systems, 8 (1982),
133-139.
[5] A. Rosenfeld, Fuzzy groups, J. Math. Anal. Appl., 35 (1971), 512-517.
[6] N. K. Saha, On $\Gamma$−semigroup II, Bull. Cal. Math. Soc., 79 (1987), 331-335.
[7] M. K. Sen, On $\Gamma$−semigroups, Proc. of the Int. Conf. on Algebra and it’s Appl., Decker
Publication, New York 301 (1981).
[8] M. K. Sen and N. K. Saha, On $\Gamma$−semigroup I, Bull. Cal. Math. Soc., 78 (1986), 180-186.
[9] L. A. Zadeh, Fuzzy sets, Inform. and Control, 8 (1965), 338-353.
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