BELKHELFA, M.; MAHI, F. Second order parallel tensors on $S$ -manifolds and semi-parallel hypersurfaces of $S$ -space forms. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 71, n. 10, p. 1422–1429, 2019. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/1524. Acesso em: 5 dec. 2025.