It is well known that the set of isomorphism classes of extensions of groups with abelian kernel is characterized by the second cohomology group. In this paper we generalise this characterization of extensions to a natural class of extensions of monoids, the cosetal extensions. An extension

中文翻译：

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一类自然类的半式扩展的求和

众所周知，具有阿贝尔核的群的扩展的同构类的集合的特征在于第二同调群。在本文中，我们将扩展的这种特征概括为类半体动物的自然扩展类，即集集扩展。扩展