1. L. E. Ballentine,Rev. Mod. Phys. 42 (4), 358 (1970).
2. J. M. Jauch,Foundations of Quantum Mechanics (Addison-Wesley, Reading, Mass., 1968).
3. E. P. Wigner,Phys. Rev. 40, 749 (1932).
4. D. Bohm,Phys. Rev. 85, 180 (1952).
5. R. P. Feynman,Quantum Mechanics and Path Integrals (McGraw-Hill, New York, 1965).