We establish conditions under which Baire measurable solutions f of $$ \Gamma (x,y,|f(x) - f(y)|) = \Phi (x,y,f(x + \phi _1 (y)),...,f(x + \phi _N (y))) $$ defined on a metrizable topological group are continuous at zero.
[5] Volkmann P., On the functional equation min{f(x + y); f(x − y)} = |f(x − f(y)|, talk at the Seminar on Functional Equations and Inequalities in Several Variables in the Silesian University Mathematics Department on January 19, 2009