On the square subgroups of decomposable torsion-free abelian groups of rank three.

The square subgroup of an abelian group which is denoted by , can be understood as a subgroup of A generated by the squares of all possible rings defined on A. Clearly, this generalizes the classical concept of a nil group. In this paper, the square subgroups of some decomposable torsion-free abelian groups are studied. In particular, we obtain new results about the square subgroups of some decomposable torsion-free abelian groups of rank three. [ABSTRACT FROM AUTHOR]