Duality Theorems on Control and Observation of Discrete-Time Infinite-Dimensional Systems. - Andrzej W. Olbrot; Andrzej Sosnowski (Math. Syst. Theory, 1981)

Remarks on the theory of implicit linear continuous-time systems. - K. Maciej Przyluski; Andrzej Sosnowski (Kybernetika, 1994)