GRANLUND, Seppo. An $L^p$-Estimate for the gradient of extremals. Mathematica Scandinavica, Berkeley, CA, United States, v. 50, p. 66–72, 1982. DOI: 10.7146/math.scand.a-11944. Disponível em: https://journals.msp.org/mscand/article/view/1704. Acesso em: 25 jul. 2026.