1. S. S. Sannikov, Ukr. Fiz. Zh.,9, 1139 (1964); Dokl. Akad. Nauk SSSR,172, 37 (1967); Yad. Fiz.,2, 570 (1965); Yad. Fiz.,4, 587 (1966).
2. S. S. Sannikov, Dokl. Akad. Nauk SSSR,178, 800 (1968);176, 801 (1967).
3. S. S. Sannikov, Dokl. Akad. Nauk SSSR,198, 297 (1971);177, 1285 (1967).
4. I. M. Gel'fand, R. A. Minlos, and Z. Ya. Shapiro, Representations of the Rotation and Lorentz Groups and their Applications, Pergamon Press, Oxford (1963).
5. J. von Neumann, Mathematical Foundations of Quantum Mechanics, Princeton (1955).