1. Functional Equations in Several Variables;Aczél,1989
2. On the d’Alembert type functional equation in Hilbert algebras;Badora;Funkcial. Ekvac.,2000
3. On the cosine-sine operator functional equations;Buche;Aequationes Math.,1971
4. Trigonometric functional equations in gevery distributions;Chung;Honam Math. J.,2008
5. Systems of trigonometric functional equations in Banach algebras;Fechner;Aequationes Math.,2009