An almost completely decomposable abelian acd group is an extension of afinite direct sum of subgroups of the additive group of rational numbers by afinite abel... » 

An almost completely decomposable abelian acd group is an extension of afinite direct sum of subgroups of the additive group of rational numbers by afinite abelian group. Examples are easy to write and are frequently used buthave been notoriously difficult to study and classify because of theircomputational nature. However a general theory of acd groups has beendeveloped and a suitable weakening of isomorphism Ladys nearisomorphism hasbeen established as the rightconcept for studying acd groups. A number ofimportant classes of acd groups has been successfully classified. Direct sumdecompositions of acd groups are preserved under nearisomorphism and the wellknown pathological decompositions can actually be surveyed in special cases. «