KIRFEL, Christoph; SELMER, Ernst S. Regular $h$-ranges and weakly pleasant $h$-bases. Mathematica Scandinavica, Berkeley, CA, United States, v. 59, p. 30–40, 1986. DOI: 10.7146/math.scand.a-12151. Disponível em: https://journals.msp.org/mscand/article/view/1521. Acesso em: 25 jul. 2026.