CARLSSON, Anders, Maz’ya, V. On Approximation in Weighted Sobolev Spaces and Self-Adjointness. MATHEMATICA SCANDINAVICA, [S. l.], v. 74, p. 111–124, 1994. DOI: 10.7146/math.scand.a-12483. Disponível em: https://tidsskrift.dk/math/article/view/12483. Acesso em: 13 aug. 2026.