Geodesic
On a class of locally Butler groups
Commentationes Mathematicae Universitatis Carolinae, Tome 32 (1991) no. 4, pp. 597-600 Cet article a éte moissonné depuis la source Czech Digital Mathematics Library

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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.
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.
Classification : 20K20, 20K27, 20K35
Keywords: Butler group; generalized regular subgroup 
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Bican, Ladislav. On a class of locally Butler groups. Commentationes Mathematicae Universitatis Carolinae, Tome 32 (1991) no. 4, pp. 597-600. http://geodesic.mathdoc.fr/item/CMUC_1991_32_4_a0/

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