Non-integrability of a Hamiltonian system, based on a problem of nonlinear vibration of an elastic string. Annual of Sofia University St. Kliment Ohridski. Faculty of Mathematics and Informatics, [S. l.], v. 99, p. 137–153, 2009. Disponível em: https://annual.uni-sofia.bg/index.php/fmi/article/view/118. Acesso em: 16 dec. 2025.