COHEN, E. Nagell’s Totient Function. MATHEMATICA SCANDINAVICA, [S. l.], v. 8, p. 55–58, 1960. DOI: 10.7146/math.scand.a-10591. Disponível em: https://www.mscand.dk/article/view/10591. Acesso em: 14 apr. 2025.