1. V. A. Khodel’ and V. R. Shaginyan, JETP Lett. 51, 553 (1990).
2. L. D. Landau, Zh. Éksp. Teor. Fiz. 30, 1058 (1956) [Sov. Phys. JETP 3, 984 (1956)]; ibid. 35, 97 (1958) [Sov. Phys. JETP 8, 70 (1959)].
3. P. Noziéres, J. Phys. I France 2, 443 (1992).
4. A. B. Migdal, Theory of Finite Fermi Systems and Applications to Atomic Nuclei, Interscience Publishers, New York, 1967 [Russian original, Nauka, Moscow, 1967].
5. Y. Sun and G. Kirczenow, Phys. Rev. Lett. 72, 2450 (1994).