1. A. Z. Capri,Nonrelativistic Quantum Mechanics (Benjamin/Cummings, Menlo Park, California, 1985), p. 194. P. Roman,Advanced Quantum Theory (Addison-Wesley, Reading, Massachusetts, 1965) p. 12.
2. M. Cini and J.-M. Levy-Leblond, eds.,Quantum Theory without Reduction (Adam Hilger, Bristol, 1990).
3. E. Prugovečki,Quantum Mechanics in Hilbert Space (Academic Press, New York 1981).
4. M. Reed and B. Simon,Methods of Modern Mathematical Physics, Vol. III: Scattering Theory (Academic Press, New York, 1979).
5. W. O. Amrein,Non-Relativistic Quantum Dynamics (Reidel, Dordrecht, 1981), pp. 100, 110, and 127.