1. S.K. Adhikari, Am. J. Phys. 54, 362 (1986)
2. F. Arnecke, H. Friedrich, P. Raab, Phys. Rev. A 78, 052711 (2008)
3. W.O. Amrein, J.M. Jauch, K.B. Sinha, Scattering Theory in Quantum Mechanics (W.A. Benjamin, Reading (Mass.), 1977)
4. T. Andersen, Phys. Reports 394, 157 (2004)
5. M. Abramowitz, I.A. Stegun (eds.), Handbook of Mathematical Functions (Dover Publications, New York, 1970)