Ladislav Bican
On a class of locally Butler groups

Comment.Math.Univ.Carolinae 32,4 (1991) 597-600.

Abstract:A torsionfree abelian group $B$ is called a Butler group if $Bext(B,T) = 0$ for any torsion group $T$. It has been shown in [DHR] that under $CH$ any countable pure subgroup of a Butler group of cardinality not exceeding $\aleph _\omega $ is again Butler. The purpose of this note is to show that this property has any Butler group which can be expressed as a smooth union $\cup _{\alpha < \mu }B_\alpha $ of pure subgroups $B_\alpha $ having countable typesets.

Keywords: Butler group, generalized regular subgroup
AMS Subject Classification: 20K20

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