On approximate n-ring homomorphisms and n-ring derivations
  Let $A,B$ be two rings and let $ X$ be an $ A-$module. An additive map $h: A\to B$ is called n-ring homomorphism if $h(\Pi^n_{i=1}a_i)=\Pi^n_{i=1}h(a_i),$ for all $a_1,a_2, ...,a_n \in {A}$. An additive map $D: A\to X$ is called $n$-ring derivation if $$D(\Pi^n_{i=1}a_i)=D(a_1)a_2... a_n+a_1D(a_2)a_3... a_n+... +a_1a_2... a_{n-1}D(a_n),$$ for all $a_1,a_2, ...,a_n \in {\mathcal A}$. In this paper we investigate the Hyers-Ulam-Rassias stability of $n$-ring homomorphisms and n-ring derivations. 
M. Eshaghi Gordji