DEAL, E. R. Quasi-Spectral Theory. MATHEMATICA SCANDINAVICA, [S. l.], v. 13, p. 188–198, 1963. DOI: 10.7146/math.scand.a-10698. Disponível em: https://www.mscand.dk/article/view/10698. Acesso em: 28 apr. 2024.