2.4 (1966)

Solved

(S. Chase). Suppose that an abelian group $A$ can be written as the union of pure subgroups $A_\alpha$, $\alpha \in \Omega$, where $\Omega$ is the first non-denumerable ordinal, $A_\alpha$ is a free abelian group of denumerable rank, and, if $\beta < \alpha$, then $A_\beta$ is a direct summand of $A_\alpha$. Does it follow that $A$ is a free abelian group?

Progress

Not always (P. A. Griffith, Pacific J. Math., 29 (1969), 279–284).

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