RIEGER, G. J. Zur Kreisfigur von Ford und Speiser. Mathematica Scandinavica, Berkeley, CA, United States, v. 55, p. 22–32, 1984. DOI: 10.7146/math.scand.a-12063. Disponível em: https://journals.msp.org/mscand/article/view/1611. Acesso em: 25 jul. 2026.