Caratterizzazione di classi di funzioni della forma F(x,y) = φ(h(x)+k(y)).
A characterization of some classes of functions F which have a representation of the form F(x,y) = φ(h(x)+k(y)) is given, when F is monotonic in each variable but not strictly monotonic. Some particular results concern classes of solutions of the bisymmetry or associativity equations.