YATUBA, K. A note on functions with a spectral gap. MATHEMATICA SCANDINAVICA, [S. l.], v. 36, p. 279–285, 1975. DOI: 10.7146/math.scand.a-11577. Disponível em: https://www.mscand.dk/article/view/11577. Acesso em: 14 apr. 2025.