BONDARENKO, V. G. Covariant derivatives of Jacobi fields on a manifold of nonpositive curvature. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 50, n. 6, p. 755–764, 1998. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4885. Acesso em: 5 dec. 2025.