1. A. I. Akhiezer and S. V. Peletminskii, Methods of Statistical Physics [in Russian], Nauka, Moscow.
2. N. N. Bogolyubov, ?Kinetic equations for electron-phonon systems,? Preprint E17-11822 [in English], JINR, Dubna (1978).
3. N. N. Bogolyubov and N. N. Bogolyubov (Jr), Fiz. Elem. Chastits At. Yadra,11, 245 (1980).
4. V. F. Los', and A. G. Martynenko, Teor. Mat. Fiz.,55, 313 (1983).
5. V. F. Los' and A. G. Martynenko, Physica (Utrecht) A,138, 518 (1986).