引入了可换群的稠密子群，并研究了它的基本性质。

Basic properties of the dense sub-semigroups in commutative groups are studied.

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对有限可换半群进行了讨论，建立了有限可换半群与有限可换群之间的关系。

This paper has made some discussions on the finite commutative semigroup. The relationship between the finite commutative semigroup and the finite commutative group is established.

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本文主要对几乎可换环上酉群的基本子群的正规性进行了研究。

This thesis mainly works on the normality of elementary subgroup of Unitary group over almost commutative rings.

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