Abstract: | We find the following necessary and sufficient conditions for Q (:=C(I+PC)−1) to -stabilize the standard linear time-invariant unity feedback system S(P, C) where P has the l.c.f. (Dpl, Npl) and the r.c.f. (Npr, Dpr); and is a principal ideal domain. (i) Q must have elements in (ii) (resp. (iii)) Q must factorize in with Dpr, (resp. Dpl) as a left (resp. right) factor and (iv) (I – QP) must factor in with Dpr, as a left factor. |