PrykarpatskyA. K., SamoilenkoA. M., & SamoilenkoV. G. (2003). Lyapunov–Schmidt Approach to Studying Homoclinic Splitting in Weakly Perturbed Lagrangian and Hamiltonian Systems. Ukrains’kyi Matematychnyi Zhurnal, 55(1), 66-74. Retrieved from https://umj.imath.kiev.ua/index.php/umj/article/view/3888