1. Abrikosov, A. A., Gor'kov, L. P. and Dzialoshinskii, I. Ya. (1965).Quantum Field Theoretical Methods in Statistical Physics. Pergamon Press, Ltd., London.
2. Bogolubov, N. N. and Shirkov, D. V. (1959).Introduction to the Theory of Quantized Fields. Interscience Publishers, Inc., New York.
3. Born, M. and Huang, K. (1954).Dynamical Theory of Crystal Lattices. Oxford University Press, New York.
4. Brandt, R. A. and Greenberg, O. W. (1969).Journal of Mathematical Physics,10, 1168.
5. Feynman, R. P. (1951).Physical Review,84, 108.