1. V.L. Ginzburg, L.D. Landau, Zh. Exp. & Teor. Fiz. 20, 1064 (1950).
2. J. Bardeen, L.N. Cooper, J.R. Schrieffer, Phys.Rev. 106, 162; ibid. 108, 1175; (1957).
3. V.L. Ginzburg, Soviet Solid State 2, 61 (1960).
4. A.P. Levanyuk, Zh. Exp. & Teor. Fiz. 36, 810 (1959).
5. L.G. Aslamazov, A.I. Larkin, Soviet Solid State 10, 875 (1968); Phys. Letters 26A, 238 (1968).