The Inverse Spectral Theory for the Ward Equation and for the 2+1 Chiral   Model
  We solve the Cauchy problem of the Ward model in light-cone coordinates using the inverse spectral (scattering) method. In particular we show that the solution can be constructed by solving a $2\times 2$ local matrix Riemann-Hilbert problem which is uniquely defined in terms of the initial data. These results are also directly applicable to the 2+1 Chiral model. 
A. S. Fokas and T. A. Ioannidou