On the Fermat-Lagrange principle for mixed smooth convex extremal problems
Ya Brinkhuis · Sbornik Mathematics · 2001
A simple geometric condition that can be attached to an extremal problem of a fairly general form included in a family of problems is indicated. This is used to demonstrate that the task of formulating a uniform condition for smooth convex problems can be satisfactorily accomplished. On the other hand, the necessity of this new condition of optimality is proved under certain technical assumptions.