Key points are not available for this paper at this time.
For pt.I see Comm. Pure Appl. Math., vol.87, p.39 (1984). New and known results on the direct and inverse scattering problems for first order systems and the associated nonlinear equations are surveyed. Included are a new method for the direct problem, a functional calculus for nonlinear evolutions, a Darboux transform for general systems, and relations to the eigenfunction expansion problem.
Beals et al. (Sun,) studied this question.