HEDBERG, Lars Inge; KILPELÄINEN, Tero. On the stability of Sobolev spaces with zero boundary values. Mathematica Scandinavica, Berkeley, CA, United States, v. 85, n. 2, p. 245–258, 1999. DOI: 10.7146/math.scand.a-18274. Disponível em: https://journals.msp.org/mscand/article/view/933. Acesso em: 24 jul. 2026.