1. Armacost, D.L.: On pure subgroups of LCA groups. Proc. Am. Math. Soc. 45(3), 414–418 (1974)
2. Armacost, D.L.: The Structure of Locally Compact Abelian Groups, Monographs and Textbooks in Pure and Applied Mathematics, p. 68. Marcel Dekker Inc., New York (1981)
3. Babieri, G., Dikranjan, D., Milan, C., Weber, H.: Topological torsion related to some recursive sequences of integers. Math. Nachr. 281(7), 930–950 (2008)
4. Bíró, A., Deshouillers, J.M., Sós, V.T.: Good approximation and characterization of subgroups of $$\mathbb{R} /\mathbb{Z} $$. Stud. Sci. Math. Hung. 38, 97–113 (2001)
5. Borel, J.-P.: Sous-groupes de $$\mathbb{R} $$ liés á la répartition modulo 1 de suites. Ann. Fac. Sci. Toulouse Math. 5(3–4), 217–235 (1983)