The FF-inclusion property and FF-convexity in normed spaces

In this paper, the FF-inclusion property of nonempty subsets in normed spaces is introduced. By applying this concept, two sufficient conditions for FF-convex sets are obtained which generalize the corresponding result from [E.A. Youness, E-convex sets, E-convex functions, and E-convex programming, J. Optim. Theory Appl. 102 (1999) 439–450].