1. The Control of Oscillations;Chernous’ko,1980
2. Asymptotic Methods of Optimal Control;Akulenko,1987
3. Mathematical Theory of Optimal Processes;Pontryagin,1969
4. Asymptotic Methods in the Theory of Non-linear Oscillations;Bogolyubov,1974
5. The Method of Averaging in the Theory of Non-linear Oscillatory Systems;Volosov,1971