1. Amrein, W.O., Pearson, D.C.: Preprint, University of Geneva. UGVA-DPT 1978/09-179 (1978)
2. Amrein, W.O., Jauch, J.M., Sinha, K.B.: Scattering theory in quantum mechanics. Reading: Benjamin (1977)
3. Green, T.A., Lanford, O.E.: J. Math. Phys.1, 139 (1960)
4. Misra, B., Speiser, D., Targonski, G.: Helv. Phys. Acta16, 963 (1963)
5. Villarroel, D.: Nuovo Cimento70A, 175 (1970)