GOOTMAN, Elliot C.; OLESEN, Dorte. Spectra of actions on type I $C^*$-algebras. Mathematica Scandinavica, Berkeley, CA, United States, v. 47, p. 329–350, 1980. DOI: 10.7146/math.scand.a-11894. Disponível em: https://journals.msp.org/mscand/article/view/1753. Acesso em: 25 jul. 2026.