1. The general theory is given in S. R. de Groot, H. A. Tolhoek and W. J. Huiskamp, Alpha, Beta and Gamma-ray Spectroscopy (Ed. K. Siegbahn, North Holland, Amsterdam 1968) p 1199. The notation used in Eq. (1) is close to that of R. J. Blin Stoyle and M. A. Grace, Handbuch der Physik 42 (Springer, Munchen) 555.
2. L. Niesen, Thesis, Leiden, Netherlands, 1971.
3. H. Pattijn, R. Coussement, G. Dumont, E. Schoeters, R. E. Silverans and L. Vanneste (Louvain) to be published,,
4. B. K. S. Koene and H. Postma, to be published in Nuclear Physics.
5. H. R. Andrews, T. F. Knott, F. M. Pipkin and D. Santry, Physics Letters 26A, 58 (1967).