1. For example, A. Akhiezer and V. Aleksin,Doklady Akad. Nauk. SSSR 92, 259 (1953); I. P. Ipatova and G. M. Eliashberg,Zh. Eksp. Teor. Fiz. 43, 1795 (1962); D. Vollhardt and P. Wölfle,Phys. Rev. Lett. 47, 190 (1981); K. S. Bedell and D. E. Meltzer,J. Low Temp. Phys. 63, 215 (1986).
2. B. Castaing and P. Nozieres,J. de Physique 40, 257 (1979).
3. A. E. Meyerovitch,J. de Physique C 7 41, C7-61 (1980), and unpublished notes.
4. A. L. Fetter and J. D. Walecka,Quantum Theory of Many Particle Systems (McGraw-Hill, New York 1968).
5. H. H. Fu and C. J. Pethick,Phys. Rev. B 14, 3837 (1976).