HÖRMANDER, Lars. Hypoelliptic Convolution Equations. MATHEMATICA SCANDINAVICA, [S. l.], v. 9, p. 178–184, 1961. DOI: 10.7146/math.scand.a-10633. Disponível em: https://tidsskrift.dk/math/article/view/10633. Acesso em: 14 aug. 2026.