CHOI, M.- duen; ELLIOT, G. A. Density of the self-adjoint elements with finite spectrum in an irrational rotation $C^*$-algebra. MATHEMATICA SCANDINAVICA, [S. l.], v. 67, p. 73–86, 1990. DOI: 10.7146/math.scand.a-12321. Disponível em: https://www.mscand.dk/article/view/12321. Acesso em: 29 apr. 2024.