Chudziak, Małgorzata. “On a Generalization of the Popoviciu Equation on Groups”. Annales Universitatis Paedagogicae Cracoviensis Studia Mathematica 9 (April 27, 2010): 49–54. Accessed October 31, 2026. https://studmath.uken.krakow.pl/article/view/13245.