1. For a review of the WKB method see, for example, M. V. Berry, K. E. Mount: Rep. Prog. Phys.35, 315 (1972) J. A. Wheeler:Studies in Mathematical Physics, Essays in Honour of Valentine Bargmann, ed. by E. H. Lieb, A. S. Wightman (Princeton Univ. Press, Princeton 1976)
2. For the fundamental role of the rectangular potential well in quantum mechanics see, for example, D. Bohm:Quantum Theory (Prentice-Hall, Englewood Cliffs 1951)
3. For a discussion of the irrigation canal, see M. Casas, H. Krivine, J. Martorell: Am. J. Phys.57, 35 (1989)
4. Throughout this paper we use dimensionless variablesx=(2??/?)1/2 q andp=(2???)?1/2 $$\tilde p$$ whereq and $$\tilde p$$ denote the dimensional coordinate and momentum of a particle of mass ? and ? is a characteristic frequency. The Schrödinger equation in these coordinates reads $$i\dot \Psi = [p^2 + V(x)]\Psi$$
5. J. Bestle, W. P. Schleich, J. A. Wheeler: Appl. Phys. B60, 289 (1995)