HEDBERG, L. I.; KILPELÄINEN, T. On the stability of Sobolev spaces with zero boundary values. MATHEMATICA SCANDINAVICA, [S. l.], v. 85, n. 2, p. 245–258, 1999. DOI: 10.7146/math.scand.a-18274. Disponível em: https://www.mscand.dk/article/view/18274. Acesso em: 6 may. 2024.