This paper examines properties and interrelations of several concepts of generalized concavity. It shows that the class of functions that are both 'generalized concave' and 'generalized convex' is ...

H. E. White, Jr., Functions with a Concave Modulus of Continuity, Proceedings of the American Mathematical Society, Vol. 42, No. 1 (Jan., 1974), pp. 104-112 ...