J. Morales and T. M. , Nonlinear Frequency Shift of an Electron Plasma Wave, Physical Review Letters, vol.7, issue.7, p.417, 1972.
DOI : 10.1063/1.1711291

L. Berk, C. E. Nielsen, and K. V. Roberts, 28 Patrick Flandrin, Time-Frequency/Time-Scale Analysis Academic Saturation process induced by vortex-merging? Phys, Phys. Fluids Plasmas, vol.13, issue.14, pp.72704-72719, 1970.