Let G be an abelian group and ◻ G its square subgroup as defined in the introduction. We show that the square subgroup of a non-homogeneous and indecomposable torsion-free group G of rank two is a pure subgroup of G and that G/◻ G is a nil group.
@article{bwmeta1.element.bwnjournal-article-doi-10_4064-cm117-1-2,
author = {A. M. Aghdam and A. Najafizadeh},
title = {Square subgroups of rank two abelian groups},
journal = {Colloquium Mathematicae},
volume = {116},
year = {2009},
pages = {19-28},
zbl = {1186.20037},
language = {en},
url = {http://dml.mathdoc.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-cm117-1-2}
}
A. M. Aghdam; A. Najafizadeh. Square subgroups of rank two abelian groups. Colloquium Mathematicae, Tome 116 (2009) pp. 19-28. http://gdmltest.u-ga.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-cm117-1-2/