1. L. D. Landau and E. M. Lifshitz, Quantum Mechanics: Nonrelativistic Theory, 3rd ed., Pergamon Press, Oxford (1977).
2. A. Pais, Proc. Cambridge Philos. Soc.,42, 45 (1946).
3. T. Titts, Zh. Eksp. Teor. Fiz.,37, 294 (1959).
4. Ta-You Wu and T. Ohmura, Quantum Theory of Scattering, Prentice-Hall London (1962).
5. G. N. Watson, A Treatise on the Theory of Bessel Functions, Cambridge (1922).