PARAMONOV, P. V.; VERDERA, J. Approximation by Solutions of Elliptic Equations on Closed Subsets of Euclidean Space. MATHEMATICA SCANDINAVICA, [S. l.], v. 74, p. 249–259, 1994. DOI: 10.7146/math.scand.a-12493. Disponível em: https://www.mscand.dk/article/view/12493. Acesso em: 29 apr. 2024.