Choczewski, B., Corovei, I. and Matkowska, A. (2004) “On some functional equations related to Steffensen’s inequality”, Annales Universitatis Paedagogicae Cracoviensis Studia Mathematica, 4, pp. 31–37. Available at: https://studmath.uken.krakow.pl/article/view/13306 (Accessed: 30 October 2026).