PURMONEN, Veikko T. On a complete initial-boundary value problem for parabolic pseudo-differential operators. Mathematica Scandinavica, Berkeley, CA, United States, v. 67, p. 97–118, 1990. DOI: 10.7146/math.scand.a-12323. Disponível em: https://journals.msp.org/mscand/article/view/1356. Acesso em: 24 jul. 2026.