PEDERSEN, G. K.; PETERSEN, N. H. Ideals in a $C^*$-Algebra. Mathematica Scandinavica, Berkeley, CA, United States, v. 27, p. 193–204, 1970. DOI: 10.7146/math.scand.a-10998. Disponível em: https://journals.msp.org/mscand/article/view/2324. Acesso em: 25 jul. 2026.