On A Characterization Of Trigonometrical And Hyperbolic Functions By Functional Equations Czeslaw Dyjak (1982) Publications de l'Institut Mathématique
On a functional equation with asymptotically unique continuous solutions. (Short Communication). E. Seneta (1976) Aequationes mathematicae
On a functional equation with asymptotically unique continuous solutions. E. Seneta (1976) Aequationes mathematicae
On the family of sets of approximate limit numbers Władysław Wilczyński (1972) Fundamenta Mathematicae