1. V. I. Arnold,Instability of dynamical systems with many degrees of freedom, Dokl. Akad. Nauk SSSR5 (1964), 581–585 (Russian)
2. G. D. Birkhoff, Dynamical systems, Amer. Math. Soc. Colloq. Publ. IX., New York, 1927
3. S. V. Bolotin,Libration motions of natural dynamical systems, Vestnik Moskov. Univ. Ser. I Mat. Mekh.6 (1978), 72–77 (Russian)
4. Libration motions of reversible Hamiltonian systems, Dissertation, Moscow State University, 1981
5. The existence of homoclinic motions, Vestnik Moskov. Univ. Ser. I Mat