Fenyő I, Pap E. ON THE FUNCTIONAL EQUATION f(x1 )+f(x2) = f(Y1) +f(Y2). Period. Polytech. Elec. Eng. [Internet]. 1981 Jan. 1 [cited 2024 May 18];25(2):115-22. Available from: https://pp.bme.hu/ee/article/view/4772