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2. A. O. Barut,Phys. Lett. A 143, 349 (1990).
3. A. O. Barut and A. Grant,Found. Phys. Lett. 3, 303 (1990).
4. For a historical discussion, see A. O. Barut, “Louis de Broglie and the single quantum particle,” in L. de Broglie,Heisenberg's Uncertainties and the Probabilistic Interpretation of Wave Mechanics, translation by A. van der Merwe (Kluwer, Dordrecht, 1990).
5. E. Schrödinger,Naturwissenschaften 14, 664 (1926).