JÓNSSON, Bjarni. On direct decompositions of torsionfree Abelian groups. Mathematica Scandinavica, Berkeley, CA, United States, v. 5, p. 230–235, 1957. DOI: 10.7146/math.scand.a-10499. Disponível em: https://journals.msp.org/mscand/article/view/2822. Acesso em: 8 sep. 2026.