“…In papers (Davison, 2001;Davison, 1974a;Davison, 1974b; Davison and Redlin, 1980) the equation (1.1) was investigated on various abstract structures. In paper (Fenyő, 1970) a Pexider version (that is functional equation with more unknown function [Aczél, 1983;Aczél and Dhombres, 1989;Kuczma, 1985;Glavosits and Lajkó, 2016]) of equation (1.1) and its locally integrable function solutions can be found. See also (Lajkó et al, 2009;Lajkó and Mészáros, 2015).…”