GALE, David; KLEE, Victor. Unique reducibility of subsets of commutative topological groups and semigroups. Mathematica Scandinavica, Berkeley, CA, United States, v. 36, p. 174–198, 1975. DOI: 10.7146/math.scand.a-11570. Disponível em: https://journals.msp.org/mscand/article/view/2047. Acesso em: 25 jul. 2026.