1. The literature on the inverse problem of scattering is extensive and we do not intend to give references to the original literature here, with a few excep tions. General references are
2. L.D. FADDEEV, Usp. Mat. Nauk 14, 57 (1959) (Translation J. Math. Phys. 4, 72 (1963))
3. V. De ALFARO and T. REGGE, Potential Scattering (North-Holland, Amsterdam, 1965), Chap. 12.
4. R.G. NEWTON, Scattering Theory of Particles and Waves, (Mc. Graw-Hill, New-York, 1966)
5. The unitarityconstraints discussed in section 3 were first investigated by