1. Functional Equations in Several Variables;Aczél,1989
2. The stability of the cosine equation;Baker;Proc. Amer. Math. Soc.,1980
3. The stability of the equation f(x+y)=f(x)+f(y);Baker;Proc. Amer. Math. Soc.,1979
4. Su una generalizzazione delle funzioni iperboliche e delle funzioni circolari;Battioni;Riv. Mat. Univ. Parma (2),1969
5. Decomposition of the Bessel functions with respect to the cyclic group of order n;Ben Cheikh;Le Matematiche,1997