Free and almost-free subsemigroups of a
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Ronald V. Book
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Article
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1973
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Elsevier Science
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English
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A subsemigroup S of a free semigroup F(Z) is almost-free if there is a free subsemigroup T such that S c T c F(2;) and TkS is finite. It is shown that it is decidable whether a subsemigroup generated by a regular subset of F(Z) is almost-free. Sufficient conditions are given such that if a family F