Szukana fraza: [Abstract = "The proposed definition of invariant zeros is compared with other commonly known definitions. It is shown that each Smith zero of the system matrix is also an invariant zero in the sense of the definition adopted in the paper. On the other hand, simple numerical examples show that the considered definition of invariant zeros and the Davison\-Wang definition are not comparable. The output\-zeroing problem for systems decouplable by state feedback is also described."]