1. K. Maki, Gapless Superconductivity, to be published inSuperconductivity, R. Parks, ed. (Marcel Dekker, New York).
2. G. Deutscher and P. G. de Gennes, Proximity Effects, to be published inSuperconductivity, R. Parks, ed. (Marcel Dekker, New York).
3. P. G. de Gennes,Superconductivity of Metals and Alloys (Benjamin, New York, 1966).
4. A. Messiah,Quantum Mechanics (North Holland, Amsterdam, 1961), p. 489.
5. C. Kittel,Introduction to Solid State Physics (Wiley, New York, 1967).