Characterizations of Warfield Groups
Warfield groups are defined to be direct summands of simply presented abelian groups. By introducing a global definition of quasi-sequentially nice subgroups we prove some characterizations of Warfield groups involving these groups, knice subgroups, and valuated coproducts. Furthermore, we exhibit a new proof of a characterization of Warfield groups in terms of nice subgroups and valuated coproducts.
Loth, P. (1998). Characterizations of Warfield groups. Journal of Algebra, 204(1), 32-41. Doi: 10.1006/jabr.1997.7367