1. Nayfeh, A. H., ?Application of the method of mutiple scales to nonlinearly coupled oscillators?. Chaptor for theLasers, Molecules, and Methods, a Volume in the Advances in Chemical Physies Series, Wiley Interscience; New York, 1988.
2. Nayfeh, A. H. and Mook, D. T.,Nonlinear Oscillations, Wiley, New York, 1979.
3. Nayfeh, A. H. and Balachandran, B., ?Modal interactions in dynamical and structural systems?,Applied Mechanics Reviews 42, 1989, 175?201.
4. Ibrahim, P. A.,Parametric Random Vibration, Wiley, New York, 1985.
5. Mettler, E and Weidenhammer, F., ?Zum Problem des kinetischen Durchschlagens schwach gekrümmter Stäbel?Ingenieur Archly 31, 1962, 421?432.