On countable extensions of primary abelian groups
Peter Vassilev Danchev (2007)
Archivum Mathematicum
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It is proved that if is an abelian -group with a pure subgroup so that is at most countable and is either -totally projective or -summable, then is either -totally projective or -summable as well. Moreover, if in addition is nice in , then being either strongly -totally projective or strongly -summable implies that so is . This generalizes a classical result of Wallace (J. Algebra, 1971) for totally projective -groups as well as continues our recent investigations...