1. D.R. Tilley, G.J. van Gurp, and C.W. Berghout, Phys.Lett. 12, 305 (1964)
2. V.L. Ginzburg, Zh.Eksp.i Teor.Fiz. 23, 236 (1952)
3. D.R. Tilley, Proc.Phys.Soc. 85, 1177 (1965)
4. L.P. Gor’kov and T.K. Melik-Barkhudarov, Soviet Phys. JETP 18, 1031 (1964)
5. C. Caroli, P.G. de Gennes, J. Matricon, Physik d. kondensierten Materie 1, 176 (1963)