@misc{Grabowski_Piotr_Circle, author={Grabowski, Piotr and Callier, Frank M.}, howpublished={online}, publisher={Zielona Góra: Uniwersytet Zielonogórski}, language={eng}, type={artykuł}, title={Circle criterion and boundary control systems in factor form: Input-output approach}, keywords={infinite-dimensional control systems, semigroups, input-output relations}, }