DIEU, Nguyen Quang; LONG, Tang van. Sublevel sets of certain extremal functions. Mathematica Scandinavica, Berkeley, CA, United States, v. 101, n. 2, p. 184–194, 2007. DOI: 10.7146/math.scand.a-15039. Disponível em: https://journals.msp.org/mscand/article/view/658. Acesso em: 24 jul. 2026.