1. E. C. G. Stueckelberg et al.,Helv. Phys. Acta 33, 727 (1960);34, 621, 675 (1961);35, 673 (1962). D. Finkelstein, J. M. Jauch, and D. Speiser,J. Math. Phys. 3, 207 (1962);4, 136, 788 (1963).
2. J. M. Jauch,Foundations of Quantum Mechanics (Addison-Wesley, Reading, Mass., 1968); V. S. Varadarajan,Geometry of Quantum Theory (D. Van Nostrand, Princeton, N.J., 1968).
3. G. Bachman,An Introduction to p-adic Numbers and Valuation Theory (Academic Press, New York, 1964).
4. O. T. O'Meara,Introduction to Quadratic Forms (Springer-Verlag, Berlin, 1963).
5. G. Cassinelli, Thesis, University of Genoa.