KATAYAMA, Yoshikazu. Remarks on a $C^*$-dynamical system. Mathematica Scandinavica, Berkeley, CA, United States, v. 49, p. 250–258, 1981. DOI: 10.7146/math.scand.a-11934. Disponível em: https://journals.msp.org/mscand/article/view/1737. Acesso em: 25 jul. 2026.