Prykarpatsky, A. K., V. G. Samoilenko, and U. Taneri. 2003. “The Reduction Method in the Theory of Lie-Algebraically Integrable Oscillatory Hamiltonian Systems”. Ukrains’kyi Matematychnyi Zhurnal 55 (2), 232-40. https://umj.imath.kiev.ua/index.php/umj/article/view/3901.