DAELE, A. Van. On the spectrum of the analytic generator. MATHEMATICA SCANDINAVICA, [S. l.], v. 37, p. 307–318, 1975. DOI: 10.7146/math.scand.a-11609. Disponível em: https://tidsskrift.dk/math/article/view/11609. Acesso em: 14 aug. 2026.