TEAM, S. Characterization of Digraphs of Right (Left) Zero Unions of Groups: Sr. Arworn, U. Knauer, N. Na Chiangmai. Thai Journal of Mathematics, [S. l.], v. 1, n. 1, p. 131–140, 2003. Disponível em: https://thaijmath2.in.cmu.ac.th/index.php/thaijmath/article/view/15. Acesso em: 2 may. 2024.