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4. P. A. M. Dirac:Principles of Quantum Mechanics, 4th Ed. (Oxford, 1958), p. 71.
5. G. L. Trigg:Quantum Mechanics (Princeton, N. J., 1964), p. 77. Indeed,J. M. Jauch:Foundations of Quantum Mechanics (Eeading, Mass., 1968), p. 206defines the time derivative of an operator to be its commutator withH.