1. P.G. de Gennes, Superconductivity of Metals and Alloys, Benjamin, New York (1966), Chapter 3, p. 76.
2. C.P. Bean, Phys. Rev. Len. 8250 (1962).
3. Y.B. Kim, C.F. Hempstead, and A.R. Stmad, Phys. Rev. 129 528 (1963).
4. A.M. Campbell, J.E. Evetts, and D. Dew-Hughes, Phil. Mag.18 313 (1968).
5. J. Bardeen, Rev. Mod. Phys. 34, 667 (1962).