Continuous solutions of the functional equation φ ( f ( x ) ) = G ( x , φ ( x ) ) for vector-valued functions φ Z. Krzeszowiak — 1969 Annales Polonici Mathematici
On differentiable solutions of the functional equation φ(f(x)) = g(x, φ(x)) for vector-valued functions Z. Krzeszowiak — 1973 Annales Polonici Mathematici
On differentiable solutions of some systems of functional equations of p-th order Z. Krzeszowiak-Dybiec — 1980 Annales Polonici Mathematici
Existence of differentiable solutions of a system of functional equations of first order Z. Krzeszowiak-Dybiec — 1980 Annales Polonici Mathematici