KEHLET, Esben T. On the Monotone Sequential Closure of a $C^*$-Algebra. MATHEMATICA SCANDINAVICA, [S. l.], v. 25, p. 59–70, 1969. DOI: 10.7146/math.scand.a-10941. Disponível em: https://tidsskrift.dk/math/article/view/10941. Acesso em: 13 aug. 2026.