This special issue, containing as many as 17 papers, is dedicated to Professor Czesław Olech, one of the most outstanding personalities in the domain of mathematical control theory. The authors,whose papers appear in this issue, are the leading specialists in the domain all over the world. many of them have been closely collaborating with Professor Czesław Olech, being his colleagues, students and friends. The issue brings quite anumber of novel results from the domain in some of its crucial problems.

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