Assertion: abelian group's subgroup | /r/HasProperty | viewed as the union of classes
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Source sentences:
text: , then the class of \(a\) is contained in \(H\), so that a normal subgroup can be viewed as the union of classes of \(G\), and conversely, any union of classes of \(G\) satisfying the group axioms form a normal subgroup of \(G\).