Effects of relativistic and ponderomotive nonlinearties on the beat wave generation of electron plasma wave and particle acceleration in non-paraxial regionPriyanka Rawat, Ram Kishor Singh, Ram Pal Sharma and Gunjan PurohitEur. Phys. J. D, 68 3 (2014) 57DOI: https://doi.org/10.1140/epjd/e2014-40643-4