by L.D. Landau and E.M. Lifshitz ; translated from the Russian by J.R. Sykes and M.J. Kearsley ; pt. 2 : hardcover, pt. 2 : flexicover. -- 3rd ed.. -- Pergamon Press, c1980. -- (Pergamon international library of science, technology, engineering and social studies . Course of theoretical physics ; v. 9, pt. 2).