1. Los Alamos Report LA-1940;E Fermi,1955
2. also in Collected Works of Enrico Fermi, Vol II, (University of Chicago, Chicago, 1965) p. 978.
3. E.A. Jackson, J.Math.Phys. 4, 551 (1963).
4. E.A. Jackson, J.Math.Phys. 4, 686 (1963).
5. J. Ford and J. Waters, J.Math.Phys. 4, 1293 (1963).