PURMONEN, Veikko T. Parbolic pseudo-differential initial-boundary value problems. Mathematica Scandinavica, Berkeley, CA, United States, v. 65, p. 221–244, 1989. DOI: 10.7146/math.scand.a-12280. Disponível em: https://journals.msp.org/mscand/article/view/1370. Acesso em: 24 jul. 2026.