STENBERG, Warren. On Weak Separation of Convex Sets and on $\alpha$-Ubiquitous Sets. Mathematica Scandinavica, Berkeley, CA, United States, v. 16, p. 55–74, 1965. DOI: 10.7146/math.scand.a-10748. Disponível em: https://journals.msp.org/mscand/article/view/2575. Acesso em: 25 jul. 2026.