A. Pourmirzaei
Department of Mathematics, Hakim Sabzevari University, P. O. Box 96179-76487, Sabzevar, Iran
[ 1 ] - ON RELATIVE CENTRAL EXTENSIONS AND COVERING PAIRS
Let (G;N) be a pair of groups. In this article, first we con-struct a relative central extension for the pair (G;N) such that specialtypes of covering pair of (G;N) are homomorphic image of it. Second, weshow that every perfect pair admits at least one covering pair. Finally,among extending some properties of perfect groups to perfect pairs, wecharacterize covering pairs of a perfect pair (G;N)...
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