GONGBAO, Li; MARTIO, O. Stability in Obstacle Problems. Mathematica Scandinavica, Berkeley, CA, United States, v. 75, p. 87–100, 1994. DOI: 10.7146/math.scand.a-12505. Disponível em: https://journals.msp.org/mscand/article/view/1171. Acesso em: 24 jul. 2026.