CUNTZ, J. The structure of multiplication and addition in simple $C^*$-algebras. MATHEMATICA SCANDINAVICA, [S. l.], v. 40, p. 215–233, 1977. DOI: 10.7146/math.scand.a-11691. Disponível em: https://www.mscand.dk/article/view/11691. Acesso em: 29 apr. 2024.