JONSSON, Bjarni. On Direct Decomposition of Torsion Free Abelian Groups. Mathematica Scandinavica, Berkeley, CA, United States, v. 7, p. 361–371, 1959. DOI: 10.7146/math.scand.a-10582. Disponível em: https://journals.msp.org/mscand/article/view/2764. Acesso em: 8 sep. 2026.