EBBESEN, Jorgen Christian Ridder. Helical maps from LCA-groups into Hilbert spaces. Mathematica Scandinavica, Berkeley, CA, United States, v. 55, p. 271–284, 1984. DOI: 10.7146/math.scand.a-12081. Disponível em: https://journals.msp.org/mscand/article/view/1593. Acesso em: 25 jul. 2026.