1. We begin by referring to the references of Chap. 1 which include a number of books concentrating on general nuclear physics. There, beta decay is presented in some detail. Because beta decay is a particularly important issue a number of books completely devoted to this topic, for example, are given: Holstein, B. (1989) Weak Interactions (Princeton University Press, Princeton, N. J .)
2. Strachan, C. (1969) The Theory of Beta Decay (Pergamon, New York)
3. Wu, C.S., Moszkowski, S.A. (1966) Beta Decay (Wiley, New York)
4. Here, we are particularly interested in the end-point of the energy spectrum giving information about a possible non-vanishing neutrino mass. This is discussed in detail by Holzschuh, E. (1992) Rep. Prog. Phys. 55, 1035
5. Holzschuh, E., Fritschi, M., Kündig, W. (1992) Phys. Lett. B287, 381