1. Aczél, J.,Lectures on functional equations and their applications. Academic Press, New York and London, 1966.
2. Barbu, V., Precupanu, Th.,Convexity and optimization in Banach spaces. Editura Academiei, Bucharest and Sijthoff & Nordhoff International Publishers, Alphen aan den Rijn, 1978.
3. Bernstein, F., Doetsch, G.,Zur Theorie der konvexen Funktionen. Math. Ann.76 (1915), 514–526.
4. Dhombres, J.,Some aspects of functional equations. Chulalongkorn University Press, Bangkok, 1979.
5. Ger, R.,Convex transformations with Banach lattice range. Stochastica11 (1), (1988).