On the classes of higher-order Jensen-convex functions and Wright-convex   functions, II
  Recently Nikodem, Rajba and W\k{a}sowicz compared the classes of n-Wright-convex functions and n-Jensen-convex functions by showing that the first one is a proper subclass of the latter one, whenever n is an odd natural number. Till now the case of even n was an open problem. In this paper the complete solution is given: it is shown that the inclusion is proper for any natural n. The classes of strongly n-Wright-convex and strongly n-Jensen-convex functions are also compared (with the same assertion). 
Jacek Mrowiec, Teresa Rajba, Szymon W\k{a}sowicz
math.CA