On classification of the Butler and almost completely decomposable groups of finite rank

An approach to the study of torsion-free Abelian groups of finite rank developed by the author in an earlier paper is applied to smaller classes of Butler groups and of almost completely decomposable groups. Bibliography:3 titles. Translated fromZapiski Nauchnykh Seminarov POMI, Vol. 227, 1995, pp. 125–139.