JÓNSSON, Bjarni. On direct decompositions of torsionfree Abelian groups. MATHEMATICA SCANDINAVICA, [S. l.], v. 5, p. 230–235, 1957. DOI: 10.7146/math.scand.a-10499. Disponível em: https://tidsskrift.dk/math/article/view/10499. Acesso em: 14 aug. 2026.