EVANS, David E. On the spectrum of a one-parameter strongly continous representation. Mathematica Scandinavica, Berkeley, CA, United States, v. 39, p. 80–82, 1976. DOI: 10.7146/math.scand.a-11645. Disponível em: https://journals.msp.org/mscand/article/view/2003. Acesso em: 25 jul. 2026.