Volume 20 includes detailed studies on vortices and nonlinear instabilities in inhomogeneous plasma and nonlocal theory of cyclotron and Cerenkov absorption in a Nonuniformly magnetized plasma Part 1: Cooperative Effects in Plasmas; B.B. Kadomtsev. 1. Preliminaries. 2. Nonlinear Waves. 3. Waves and Particles. 4. Plasma in a Magnetic Field. 5. Linear Waves. Part 2: Relativistic Interaction of Laser Pulse With Plasmas; S.V. Bulanov, F. Califano, G.I. Dudnikova, T.Zh. Esirkepov, I.N. Inovenkov, F.F. Kamenets, T.V. Liseikina, M. Lontano, K. Mima, N. M. Naumova, K. Nishihara, F. Pegoraro, H. Ruhl, A.S. Sakharov, Y. Sentoku, V.A. Vshivkov, V.V. Zhakhovskii. Introduction. 1. Relativistically strong electromagnetic waves in underdense plasmas. 2. Acceleration of charged particles and photons. 3. Filamentation of the laser light and magnetic interaction of filaments and electromagnetic radiation. 4. Relativistic solitons. 5. Interactions of an ultrashort, relativistically strong, laser pulse with an overdense plasma. 6. Nonlinear interactions of laser pulses with a foil. 7. Coulomb explosion of a cluster irradiated by a high intensity laser pulse. 8. Conclusions. References