KATRE, S. A.; RAJWADE, A. R. On the Jacobsthal sum $\phi_9(a)$ and the related sum $\psi_9(a)$. MATHEMATICA SCANDINAVICA, [S. l.], v. 53, p. 193–202, 1983. DOI: 10.7146/math.scand.a-12026. Disponível em: https://www.mscand.dk/article/view/12026. Acesso em: 29 apr. 2024.