GUPTA, S.; HOLUBOWSKI, W. On 2-Symmetric Words in Nilpotent Groups. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 54, n. 7, p. 1020–1024, 2002. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4142. Acesso em: 7 apr. 2025.