1. A. B. Migdal, Zh. Eksp. Teor. Fiz. 34 (1958) 1438
2. A. B. Migdal, Soy. Phys. JETP 34 (1958) 996
3. D. J. Scalapino, in Superconductivity,ed. R. D. Parks (Marcel Dekker, New York, 1969) voll, p.449.
4. S. K. Joshi and A. K. Rajagopal, in Solid State Physics, eds. F. Seitz, D. Turnbull, and H. Ehrenreich ( Academic, New York, 1968 ) vol. 22, p. 159.
5. G. Grimvall, The Electron-Phonon Interaction in Metals ( North-Holland, Amsterdam, 1981 ).