THOMÉE, V. Locally Cogent Boundary Operators. MATHEMATICA SCANDINAVICA, [S. l.], v. 7, p. 5–32, 1959. DOI: 10.7146/math.scand.a-10558. Disponível em: https://www.mscand.dk/article/view/10558. Acesso em: 6 may. 2024.