PURMONEN, Veikko T. Parbolic pseudo-differential initial-boundary value problems. MATHEMATICA SCANDINAVICA, [S. l.], v. 65, p. 221–244, 1989. DOI: 10.7146/math.scand.a-12280. Disponível em: https://tidsskrift.dk/math/article/view/12280. Acesso em: 14 aug. 2026.