CHOCZEWSKI, B.; COROVEI, I.; MATKOWSKA, A. On some functional equations related to Steffensen’s inequality. Annales Universitatis Paedagogicae Cracoviensis Studia Mathematica, [S. l.], v. 4, p. 31–37, 2004. Disponível em: https://studmath.uken.krakow.pl/article/view/13306. Acesso em: 30 oct. 2026.