  According to V.P.Potapov, a classical interpolation problem can be
reformulated in terms of a so-called Fundamental Matrix Inequality (FMI). To
show that every solution of the FMI satisfies the interpolation problem, we
usualy have to transform the FMI in some special way. In this paper the number
of of transformations of the FMI which come into play are motivated and
demonstrated by simple, but typical examples.
