AMEUR, Y. A note on a theorem of Sparr. Mathematica Scandinavica, Berkeley, CA, United States, v. 94, n. 1, p. 155–160, 2004. DOI: 10.7146/math.scand.a-14435. Disponível em: https://journals.msp.org/mscand/article/view/784. Acesso em: 24 jul. 2026.