  In this paper we show that every inner divisor of the operator-valued
coordinate function, $zI_E$, is a Blaschke-Potapov factor. We also introduce a
notion of operator-valued "rational" function and then show that $\Delta$ is
two-sided inner and rational if and only if it can be represented as a finite
Blaschke-Potapov product; this extends to operator-valued functions the
well-known result proved by V.P. Potapov for matrix-valued functions.
