OJALA, Timo. Sums of roots of unity. Mathematica Scandinavica, Berkeley, CA, United States, v. 37, p. 83–101, 1975. DOI: 10.7146/math.scand.a-11590. Disponível em: https://journals.msp.org/mscand/article/view/2083. Acesso em: 25 jul. 2026.