I. Introduction
Pseudo-linear algebra [2], [3], also known as Ore algebra, is the study of common properties of linear ordinary differential, difference, shift and other type of operators, expressed in terms of the skew polynomials. In [1] pseudo-linear algebra has been introduced into the control community and applied to define the transfer function and study its basic properties in a unified manner both for continuous-and discrete-time nonlinear systems as well for less conventional discrete-time system descriptions in terms of difference, -shift and difference operators. Note that the difference operator description provides a smooth transition from sampled-data algorithms to their continuous-time counterparts [4].