Copyright © 2007 Elsevier Inc. All rights reserved.
Notes on “the lower and upper approximations in a fuzzy group” and “rough ideals in semigroups”
Received 23 March 2005;
revised 13 November 2006;
accepted 5 December 2006.
Available online 22 December 2006.
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Abstract
In this note, we show by examples that Propositions 2.4 and 2.5 in [N. Kuroki, P.P. Wang, The lower and upper approximations in a fuzzy group, Information Sciences 90 (1996) 203] and Theorem 2.5 in [N. Kuroki, Rough ideals in semigroups, Information Sciences 100 (1997) 139] are incorrect and offer their modified versions.
Keywords: Rough set; Group; Normal subgroup; Ring; Ideal







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