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2. A. D. Alexandrov:Leningrad University Herald (in Russian),2, 67 (1949).
3. L. de Broglie:Einführung in die Wellenmechanik (Leipzig, 1929).
4. E. Fermi:Notes on Quantum Mechanics (in Russian) (Moscow, 1965).
5. E. Schrödinger:Vier Vorlesungen über Wellenmechanik (Berlin, 1928).