KLEE, V. L. Jr. The structure of semispaces. Mathematica Scandinavica, Berkeley, CA, United States, v. 4, p. 54–64, 1956. DOI: 10.7146/math.scand.a-10455. Disponível em: https://journals.msp.org/mscand/article/view/2864. Acesso em: 8 sep. 2026.