  A general interpolation problem with operator argument is studied for
functions f from the de Branges-Rovnyak space H(s) associated with an analytic
function s mapping the open unit disk D into the closed unit disk. The
interpolation condition is taken in the Rosenblum-Rovnyak form f(A)c = b (with
a suitable interpretation of f(A)c) for given Hilbert space operator A and two
vectors b; c from the same space.
