SamoilenkoV. G. 1994. “Quasiinvariant Deformations of Invariant Submanifolds of Hamiltonian Dynamical Systems”. Ukrains’kyi Matematychnyi Zhurnal 46 (8), 1043–1054. https://umj.imath.kiev.ua/index.php/umj/article/view/5657.