HEINONEN, Juha; KILPELÄINEN, Tero. Polar sets for supersolutions of degenerate elliptic equations. Mathematica Scandinavica, Berkeley, CA, United States, v. 63, p. 136–150, 1988. DOI: 10.7146/math.scand.a-12229. Disponível em: https://journals.msp.org/mscand/article/view/1434. Acesso em: 24 jul. 2026.