1. T. D. Lee,Phys. Rev. 95, 1329 (1954).
2. K. O. Friedrichs,Commun. Pure Appl. Math. 1, 361 (1950).
3. L. P. Horwitz and J.-P. Marchand,Rocky Mountain J. Math. 1, 225 (1971).
4. I. Segal and L. P. Horwitz,Helv. Phys. Acta 51, 685 (1978); W. Baumgartel,Math. Nachr. 75, 133 (1978); G. Parravicini, V. Gorini, and E. C. G. Sudarshan,J. Math. Phys. 21, 2208 (1980); T. Bailey and W. C. Schieve,Nuovo Cimento A 47, 231 (1978); A. Bohm,Quantum Mechanics: Foundations and Applications, Springer, Berlin (1986); A. Bohm, M. Gadella, and G. B. Mainland,Am. J. Phys. 57, 1103 (1989).
5. A. Bohm,The Rigged Hilbert Space and Quantum Mechanics (Springer Lecture Notes on Physics78, Berlin, 1978); I. M. Gel'fand and N. Ya. Vilenkin,Generalized Functions, Vol. 4 (Academic, New York, 1964).