ALMKVIST, Gert. Stability of Linear Differential Equations in Banach Algebras. Mathematica Scandinavica, Berkeley, CA, United States, v. 14, p. 39–44, 1964. DOI: 10.7146/math.scand.a-10704. Disponível em: https://journals.msp.org/mscand/article/view/2595. Acesso em: 25 jul. 2026.