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2. Some properties of the Hessian matrix of a strictly convex function;Bernstein;J. Reine Angew. Math.,1962
3. Convex Cones, Sets, and Functions, mimeographed lecture notes from Princeton University;Fenchel,1953
4. Nonlinear Programming;Mangasarian,1969
5. Some properties of concave functions;Newman;J. Economic Theory,1969