1. [1] H. Alzer, On an integral inequality for concave functions, Acta. Sci. Math., vol. 56, 1992, 79-82.
2. [2] S. Barza, C. P. Niculescu, Integral equations for concave functions, Publ. Math. Debrecen, vol. 68, 2006, 139-159.
3. [3] J. Brzdek, D. Popa, I. Raşa, B. Xu, Ulam stability of Operators, Academic Press, Elsevier, 2018.
4. [4] A. M. Fink, M. Jodeit Jr., Jensen inequalities for functions with monotonicities, Aeq. Mathematicae, vol. 40, 1990, 26-43.
5. [5] M. Petschke, Extremalstrahlen konvexer Kegel un komplementäre Ungleichungen, Dissertation Darmstadt, 1989.