1. “Linear and Nonlinear Waves”;Whitham,1974
2. “Perturbation Methods”;Nayfeh,1973
3. Crawford, F.W., Rev. Mod. Phys. (in preparation).
4. Lagrangian approach to non-linear wave interactions in a warm plasma
5. Kim, H. and Crawford, F.W., Stanford University Institute for Plasma Research Report No. 763, (1978).