ORLOV, I. V. Elimination of Jacobi equation in extremal variational problems. Methods of Functional Analysis and Topology, [S. l.], v. 17, n. 4, p. 341–349, 2011. Disponível em: https://zen.imath.kiev.ua/index.php/mfat/article/view/498. Acesso em: 16 dec. 2025.