1. Convex Analysis and Variational Problems;Ekeland,1976
2. An Introduction to the Theory of Functional Equations and Inequalities;Kuczma,1985
3. On the monotonicity of the gradient of a convex function;Minty;Pacific J. Math.,1964
4. A characterization of midpoint-quasiaffine functions;Nikodem;Publ. Math. Debrecen,1998
5. Convex Functions;Roberts,1973