Grau, J.M. (2015) “Variations on Giuga Numbers and Giuga’s Congruence”, Ukrains’kyi Matematychnyi Zhurnal, 67(11), pp. 1573–1578. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/2091 (Accessed: 5 December 2025).