1. A. Messiah:Quantum Mechanics, Chap. XIV (Amsterdam, 1962).
2. L. I. Schiff:Quantum Mechanics, Chap. 10 (New York, N. Y., 1968).
3. E. Merzbacher:Quantum Mechanics, Chap. 18 (New York, N. Y., 1961).
4. A. M. L. Messiah andO. W. Greenberg:Phys. Rev.,136, B 248 (1964).
5. M. D. Girardeau:Phys. Rev.,139, B 500 (1965).