HÖRMANDER, L. On the Uniqueness of the Cauchy Problem. MATHEMATICA SCANDINAVICA, [S. l.], v. 6, p. 213–225, 1958. DOI: 10.7146/math.scand.a-10546. Disponível em: https://www.mscand.dk/article/view/10546. Acesso em: 3 may. 2024.