Lysenko, A., Volk, I., Serozhko, A. and Rybalko, O. 2018. MULTIPLE THREE-WAWE RESONANCES IN TWO-STREAM FREE-ELECTRON LASER WITH A HELICAL ELECTRON BEAM. Information and Telecommunication Sciences. 1 (Jul. 2018), 58–64. DOI:https://doi.org/10.20535/2411-2976.12018.58-64.