LoveikinYu. V., and ParasyukI. O. “Invariant Tori of Locally Hamiltonian Systems Close to Conditionally Integrable Systems”. Ukrains’kyi Matematychnyi Zhurnal 59, no. 1 (January 25, 2007): 71–98. Accessed November 24, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/3292.