AHMED KHALEL, L.; JASIM MOHAMMED, A. Kinds of crossed modules. Journal of Education and Science (JES), [S. l.], v. 22, n. 2, p. 354–369, 2009. DOI: 10.33899/edusj.2009.57689. Disponível em: https://ojs.uomosul.edu.iq/index.php/edusj/article/view/23496. Acesso em: 6 aug. 2025.