EVANS, D. E. On the spectrum of a one-parameter strongly continous representation. MATHEMATICA SCANDINAVICA, [S. l.], v. 39, p. 80–82, 1976. DOI: 10.7146/math.scand.a-11645. Disponível em: https://www.mscand.dk/article/view/11645. Acesso em: 4 may. 2024.