1. A. Berman and R.J. Plemmons, Nonnegative matrices in the mathematical sciences, Academic Press, New York (NY ), (1979).
2. M. Bisiacco, E. Fornasini, and G. Marchesini, 2D partial fraction expansions and minimal commutative realizations, IEEE Trans. Circ. Sys. 35 (1988), pp. 1533–1538.
3. M. Fliess, Un outil algébrique: Les séries formelles non commutatives, Springer Lect.Notes in Econ. Math. Sys. 131, (1975), pp. 122–149.
4. E. Fornasini and G. Marchesini, Doubly indexed dynamical systems, Math. Sys. Theory 12, (1978), pp. 59–72.
5. E. Fornasini and G. Marchesini, Properties of pairs of matrices and state-models for 2D systems, In C.R.Rao, editor, Multivariate Analysis: Future Directions. North Holland Series in Probability and Statistics 5, (1993), pages 131–80.