On smoothness of generalized quasiperiodic solutions of Lagrangian systems on Riemannian manifolds of non-positive curvature. Neliniini Kolyvannya, [S. l.], v. 2, n. 2, p. 180–193, 1999. Disponível em: https://twinhead.imath.kiev.ua/index.php/nosc/article/view/53. Acesso em: 22 jan. 2026.