[1] H. H. Rosenbrock: State-space and Multivariate Theory. Nelson, London 1970.
[2] P. A. Fuhrmann: 
On strict system equivalence and similarity. Internat. J. Control 25 (1977), 5-10. 
MR 0472162 | 
Zbl 0357.93009[3] L. A. Pernebo: 
Notes on strict system equivalence. Internat. J. Control 25 (1977), 21-38. 
MR 0472164[4] M. Morf: Extended system and transfer function matrices and system equivalence. In: Proc. of the 1975 IEEE Conference on Decision and Control, Houston, Texas 1975.
[6] C. T. Chen: Linear System Theory and Design. Holt, Rinehart and Winston, New York 1984.
[7] F. M. Callier, C. A. Desoer: Multivariable Feedback Systems. Springer-Verlag, New York 1982.
[8] O. M. Grasselli, A. Tornambe: 
On obtaining a realization of a polynomial matrix description of a system. IEEE Trans. Automat. Control 37 (1992), 6, 852-856. 
MR 1164565 | 
Zbl 0760.93002[9] O. M. Grasselli S. Longhi, A. Tornambe: A polynomial approach to deriving a state-space model of a periodic process described by difference equations. In: Second Internat. Symposium on Implicit and Robust Systems, Warsaw 1991.
[10] O. M. Grasselli S. Longhi, A. Tornambe: 
A polynomial approach to deriving a state-space model of a periodic process described by difference equations. Circuit Systems Signal Process., to appear. 
MR 1259601[11] O. M. Grasselli, S. Longhi: 
Finite zero structure of linear periodic discrete-time systems. Internat. J. Systems Sci. 22 (1991), 10, 1785-1806. 
MR 1128912 | 
Zbl 0743.93047[12] O. M. Grasselli, S. Longhi: 
The geometric approach for linear periodic discrete-time systems. Linear Algebra Appl. 755 (1991), 27-60. 
MR 1126434 | 
Zbl 0758.93044[13] O. M. Grasselli, S. Longhi: 
Robust tracking and regulation of linear  periodic discrete-time systems. Internat. J. Control 54 (1991), 3, 613-633. 
MR 1117838 | 
Zbl 0728.93065