• Communications of the Korean Mathematical Society
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• v.31 no.1
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• pp.17-25
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• 2016

The notion of hesitant fuzzy semigroups with two frontiers is introduced, and related properties are investigated. Relations between a hesitant fuzzy semigroups with a frontier and a hesitant fuzzy semigroups with two frontiers are discussed. It is shown that the hesitant intersection of two hesitant fuzzy semigroups with two frontiers is a hesitant fuzzy semigroup with two frontiers. We provide an example to show that the hesitant union of two hesitant fuzzy semigroups with two frontiers may not be a hesitant fuzzy semigroup with two frontiers.

• Annals of Fuzzy Mathematics and Informatics
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• v.16 no.3
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• pp.261-284
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• 2018

In this paper, we recall the definition of soft set, fuzzy soft set, hesitant fuzzy set and hesitant fuzzy soft set and some of their examples. We define the concept of hesitant fuzzy soft multiset which combines hesitant fuzzy soft set and soft multiset theory. We also define basic terms in hesitant fuzzy soft multiset with relevant examples. Some basic operations such as restricted intersection, extended intersection, union, restricted union, AND-product and OR-product and their properties are given, supported with illustrative examples. We finally establish some important results, including De Morgan's inclusions and laws.