Bohdan Zelinka, katedra diskretni matematiky a statistiky Technicke university, Voronezska 13, 460 01 Liberec
Abstract: A subtraction semigroup is a semigroup $(A,\ldotp,-)$ with a further operation "$-$" added, called subtraction and satisfying certain axioms. The paper concerns a problem by B. M. Schein concerning the structure of multiplication in a subtraction semigroup.
Keywords: subtraction semigroup, subtraction algebra, Boolean algebra
Classification (MSC91): 20M20, 06E05
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