1. Certain Problems of the Theory of Non-linear Oscillations;Malkin,1956
2. Stability in resonance cases;Kunitsyn,1979
3. On the stability of the periodic solution of a canonical system with one degree of freedom, in the case of a principal resonance;Merman,1963
4. Libration Points in Celestial Mechanics and Cosmic Dynamics;Markeyev,1978
5. On the stability of a non-autonomous Hamiltonian system under a parametric resonance of essential type;Ivanov;PMM,1980