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2. Synthesis of a nonlinear dynamic vibration absorber;Roberson;J Franklin Inst B,1952
3. On non-linear differential equations of the second order: I;Cartwright,1945
4. The dynamics of goal-directed rhythmical aiming;Mottet;Biol Cybern,1999
5. The duffing equation: nonlinear oscillators and their behaviour;Kovacic,2011