HÖRMANDER, Lars. On the Uniqueness of the Cauchy Problem. Mathematica Scandinavica, Berkeley, CA, United States, v. 6, p. 213–225, 1958. DOI: 10.7146/math.scand.a-10546. Disponível em: https://journals.msp.org/mscand/article/view/2802. Acesso em: 25 jul. 2026.