VESTERSTROM, Jorgen. On the Homomorphic Image of the Center of a $C^*$-Algebra. Mathematica Scandinavica, Berkeley, CA, United States, v. 29, p. 134–136, 1971. DOI: 10.7146/math.scand.a-11040. Disponível em: https://journals.msp.org/mscand/article/view/2315. Acesso em: 25 jul. 2026.