EARLE, Clifford J. Some remarks on the Beltrami equation. Mathematica Scandinavica, Berkeley, CA, United States, v. 36, p. 44–48, 1975. DOI: 10.7146/math.scand.a-11561. Disponível em: https://journals.msp.org/mscand/article/view/2051. Acesso em: 25 jul. 2026.