LEWANDOWSKI, A. A Generalization of the Annulus Formula for the Relative Extremal Function. MATHEMATICA SCANDINAVICA, [S. l.], v. 115, n. 1, p. 69–84, 2014. DOI: 10.7146/math.scand.a-18003. Disponível em: https://www.mscand.dk/article/view/18003. Acesso em: 28 mar. 2024.