JONSSON, Bjarni. On Direct Decomposition of Torsion Free Abelian Groups. MATHEMATICA SCANDINAVICA, [S. l.], v. 7, p. 361–371, 1959. DOI: 10.7146/math.scand.a-10582. Disponível em: https://tidsskrift.dk/math/article/view/10582. Acesso em: 14 aug. 2026.