M. Balcerowski, On a problem of T. Szostok on functions with monotonic differences, Aequationes Math. 85 (2013), no. 1–2, 165–167.
Google Scholar

N.G. de Brujin, Functions whose differences belong to a given class, Nieuw Arch. Wiskunde (2) 23 (1951), 194–218.
Google Scholar

M. Kuczma, An Introduction to the Theory of Functional Equations and Inequalities, PWN – Uniwersytet Śląski, Warszawa-Kraków-Katowice, 1985.
Google Scholar

G. Maksa and Z. Páles, Decomposition of higher-order Wright-convex functions, J. Math. Anal. Appl. 359 (2009), no. 2, 439–443.
Google Scholar

C.T. Ng, Functions generating Schur-convex sums, in: W. Walter (ed.), General Inequalities, 5 (Oberwolfach, 1986), International Series of Numerical Mathematics, 80, Birkhäuser, Basel-Boston, 1987, pp. 433–438.
Google Scholar

Z. Páles, An elementary proof for the decomposition theorem of Wright convex functions, Ann. Math. Sil 34 (2020), no. 1, 142–150.
Google Scholar

T. Rajba, A generalization of multiple Wright-convex functions via randomization, J. Math. Anal. Appl. 388 (2012), no. 1, 548–565.
Google Scholar

T. Szostok, 4. Problem. Report of Meeting. The Fifth Katowice-Debrecen Winter Seminar on Functional Equations and Inequalities, February 2–5, 2005, Bedlewo, Poland, Ann. Math. Sil. 19 (2005), 65–78.
Google Scholar

T. Szostok, 5. Problem. Report of Meeting. The Forty-fourth International Symposium on Functional Equations, May 14–20, 2006, Lousiville, USA, Aequationes Math. 73 (2007), no. 1–2, 172–200.
Google Scholar

T. Szostok, On !-convex functions, in: H. Hudzik et al. (eds.), Function Spaces IX, Banach Center Publications, 92, Polish Academy of Sciences, Institute of Mathematics, Warsaw, 2011, pp. 351–359.
Google Scholar

E.M. Wright, An inequality for convex functions, Amer. Math. Monthly 61 (1954), 620–622.
Google Scholar