LEWANDOWSKI, Arkadiusz. A Generalization of the Annulus Formula for the Relative Extremal Function. Mathematica Scandinavica, Berkeley, CA, United States, v. 115, n. 1, p. 69–84, 2014. DOI: 10.7146/math.scand.a-18003. Disponível em: https://journals.msp.org/mscand/article/view/415. Acesso em: 24 jul. 2026.