1. F. Harris, Private communication (Bell Textron).
2. Principles of Aeroelasticity;Bisplinghoff,1962
3. Recent developments in rotary wing aeroelasticity;Friedmann;J. Aircraft,1977
4. Solutions of nonlinear hyperbolic equations at resonance;Cesari;Nonlinear Anal.,1982
5. A. Haraux, Nonlinear evolution equations—Global behaviour of solutions. In Lecture Notes in Mathematics, Vol. 841. Springer-Verlag, New York.