Recovery of Dirac system from the rectangular Weyl matrix function
  Weyl theory for Dirac systems with rectangular matrix potentials is non-classical. The corresponding Weyl functions are rectangular matrix functions. Furthermore, they are non-expansive in the upper semi-plane. Inverse problems are treated for such Weyl functions, and some results are new even for the square Weyl functions. High energy asymptotics of Weyl functions and Borg-Marchenko type uniqueness results are derived too. 
B. Fritzsche, B. Kirstein, I.Ya. Roitberg, A.L. Sakhnovich
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