THOMÉE, V. Existence Proofs for Mixed Problems for Hyperbolic Differential Equations in Two Independent Variables by Means of the Continuity Method. MATHEMATICA SCANDINAVICA, [S. l.], v. 6, p. 5–32, 1958. DOI: 10.7146/math.scand.a-10531. Disponível em: https://www.mscand.dk/article/view/10531. Acesso em: 29 apr. 2024.