Iliev, Hristo. “On the Non-Integrability of a Hamiltonian System Resulting from a Problem for Elastic String”. Ann. Sofia Univ. Fac. Math. and Inf. 88 (December 12, 1996): 57–69. Accessed November 24, 2024. https://annual.uni-sofia.bg/index.php/fmi/article/view/379.