BROWN, Lawrence G.; PEDERSEN, Gert K. Approximation and convex decomposition by extremals in a $C^*$-algebra. Mathematica Scandinavica, Berkeley, CA, United States, v. 81, p. 69–85, 1997. DOI: 10.7146/math.scand.a-12866. Disponível em: https://journals.msp.org/mscand/article/view/1039. Acesso em: 25 jul. 2026.