2Y.Z. Chen. Evaluation of motion of the Duffing equation from its general properties, JORUNAL OF SOUND AND VIBRATION, Volume: 264, Issue: 2, July 3, 2003, pp. 491-497
3B.R.Nana Nbendjo, R. Tchoukuegno, p. Woafo. Active control with delay of vibration and chaos in a double - well Duffing oscillator, CHAOS SOLITONS & FRACTALS, Volume: 18, Issue: 2, October, 2003, pp. 345-353