MAGNUS, Robert. On the Multiplicity of an Analytic Operator-Valued Function. Mathematica Scandinavica, Berkeley, CA, United States, v. 77, p. 108–118, 1995. DOI: 10.7146/math.scand.a-12552. Disponível em: https://journals.msp.org/mscand/article/view/1120. Acesso em: 25 jul. 2026.