The so-called minimal design problem (or MDP) of linear system theory is to find a proper minimal degree rational matrix solution of the equation H(z)D(z)=N(z), where {N(z),D(z)} are given pxr and mxr polynomial matrices with D(z) of full rank r=
['S. Y. Kung', 'Thomas Kailath']
Brief paper: Fast projection methods for minimal design problems in linear system theory