“…We are concerned with necessary conditions for a solution to P. If F(t, x) admits a parametrization, i.e. there exist a set U and a function f(t, x, u) such that F(t, x)=[ f(t, x, u) : u # U] and if certain regularity conditions are satisfied then the maximum principle and its various generalizations (see [26,30]) concerning the control system defined by ( f, U ) provide necessary conditions for a solution to P. However, for a nonconvex-valued multifunction F it is very difficult to determine whether such a parametrization exists. On the other hand, a variant of Lojasiewicz'es parametrization theorem [17] shows that under fairly general conditions such a parametrization exists when F is convex-valued (Section 4).…”