HALBERG, C. J. A. ,. Jr.; SAMUELSSON, A. On the Fine Structure of Spectra. MATHEMATICA SCANDINAVICA, [S. l.], v. 29, p. 37–49, 1971. DOI: 10.7146/math.scand.a-11032. Disponível em: https://tidsskrift.dk/math/article/view/11032. Acesso em: 14 aug. 2026.