1. L. V. Keldysh, Doktoral Dissertation (Lebedev Institute, Moscow, 1965).
2. A. A. Abrikosov, L. P. Gorkov, and I. E. Dzyaloshinski, Methods of Quantum Field Theory in Statistical Physics (Prentice-Hall, Englewood Cliffs, NJ, 1963).
3. A. L. Efros, Zh. Eksp. Teor. Fiz. 59, 880 (1970) [Sov. Phys. JETP 32, 479 (1971)].
4. M. E. Raikh and T. V. Shahbazyan, Phys. Rev. B 47, 1522 (1993).
5. M. N. Kiselev, K. Kikoin, Y. Avishai, and J. Richert, Phys. Rev. B 74, 115306 (2006).