P. SREENIVASULU REDDY. Applications of Semigroups. Global Journal of Science Frontier Research, [S. l.], v. 15, n. F3, p. 17–25, 2015. Disponível em: https://journalofscience.org/index.php/GJSFR/article/view/1541. Acesso em: 8 may. 2024.