PrykarpatskyY. A., & SamoilenkoA. M. (1999). Investigation of invariant deformations of integral manifolds of adiabatically perturbed completely integrable Hamiltonian systems. II. Ukrains’kyi Matematychnyi Zhurnal, 51(11), 1513–1528. Retrieved from https://umj.imath.kiev.ua/index.php/umj/article/view/4753