1. R. de L. Kronig, W.J. Penney: Proc. Roy. Soc. London A130, 499 (1930)
2. A. Nussbaum: Semiconductor Device Physics (Prentice-Hall, Englewood Cliffs, NJ 1962) Sects.1.9,13
3. R.A. Smith: Wave Mechanics of Crystalline Solids, 2nd ed. (Chapman and Hall, London 1969) Sect.6.2
4. J.P. McKelvey: Solid-State and Semiconductor Physics (Harper and Row, New York 1966) Sect.8.6
5. E.O. Kane: J. Phys. Chem. Solids 1, 249 (1957)