“…The potentials in (4.6) occur in χ 1 . The D-bar data, or departure from analyticity of χ, corresponds to spectral data in a sometimes complicated way and we refer to [1,5,6,9,11,13,16,20,22,23] for more on this. Now one expects some connections between inverse scattering for KdV and the dKdV theory since ǫx = X means e.g.…”