CHENG, C.-M. TWO RESULTS ON $C$-CONGRUENCE NUMERICAL RADII. Tamkang Journal of Mathematics, [S. l.], v. 21, n. 1, p. 59–64, 1990. DOI: 10.5556/j.tkjm.21.1990.4695. Disponível em: https://journals.math.tku.edu.tw/index.php/TKJM/article/view/4695. Acesso em: 3 may. 2024.