1. John von Neumann,Mathematical Foundations of Quantum Mechanics (Princeton University Press, Princeton, 1955), Chaps. V and VI.
2. E. P. Wigner, inQuantum Theory of Measurement, J. A. Wheeler and W. H. Zurek, eds. (Princeton University Press, Princeton, New Jersey, 1983), p. 260.
3. ?... The possibility of finding a mathematical expression for the outcome of the measurement of an operator obviously does not guarantee the possibility of such a measurement....? (Ibid.,, p. 275.)
4. ?... To repeat, all this is theory and there is no mathematical guarantee that even a transition probability into an arbitrary state can be measured. In order to guarantee the possibility of such a measurement, one would have to describe a way to do it. The mathematical theory of measurement, as formulated first by von Neumann, but now generally accepted, ingenious as it is, does not do that....? (Ibid.,, p. 276.)
5. See also the discussion of the theorem that: ?... only quantities which commute with all additive conserved quantities are precisely measurable? (ibid., E. P. Wigner, inQuantum Theory of Measurement, J. A. Wheeler and W. H. Zurek, eds. (Princeton University Press, Princeton, New Jersey, 1983), p. 293) and of super selection rules (ibid., E. P. Wigner, inQuantum Theory of Measurement, J. A. Wheeler and W. H. Zurek, eds. (Princeton University Press, Princeton, New Jersey, 1983), p. 305).