KEHLET, Esben T. On the Monotone Sequential Closure of a $C^*$-Algebra. Mathematica Scandinavica, Berkeley, CA, United States, v. 25, p. 59–70, 1969. DOI: 10.7146/math.scand.a-10941. Disponível em: https://journals.msp.org/mscand/article/view/2403. Acesso em: 25 jul. 2026.