Weyl-Titchmarsh functions of vector-valued Sturm-Liouville operators on   the unit interval
  The matrix-valued Weyl-Titchmarsh functions $M(\lambda)$ of vector-valued Sturm-Liouville operators on the unit interval with the Dirichlet boundary conditions are considered. The collection of the eigenvalues (i.e., poles of $M(\lambda)$) and the residues of $M(\lambda)$ is called the spectral data of the operator. The complete characterization of spectral data (or, equivalently, $N\times N$ Weyl-Titchmarsh functions) corresponding to $N\times N$ self-adjoint square-integrable matrix-valued potentials is given, if all $N$ eigenvalues of the averaged potential are distinct. 
Dmitry Chelkak, Evgeny Korotyaev