KRAPEŽ, Aleksandar; SHCHERBACOV, Victor A. Quasigroups, Units and Belousov’s Problem # 18. Armenian Journal of Mathematics, Yerevan, Armenia, v. 11, n. 9, p. 1–27, 2019. Disponível em: https://armjmath.sci.am/index.php/ajm/article/view/210. Acesso em: 11 may. 2025.