WIDMAN, K.- ove. Inequalities for the Green Function and Boundary Continuity of the Gradient of Solutions of Elliptic Differential Equations. MATHEMATICA SCANDINAVICA, [S. l.], v. 21, p. 17–37, 1967. DOI: 10.7146/math.scand.a-10841. Disponível em: https://www.mscand.dk/article/view/10841. Acesso em: 27 apr. 2024.