Xu, Tian Zhou, Generalized Hyers-Ulam stability of a general mixed additive-cubic functional equation in quasi-Banach spaces, Acta mathematica Sinica. English series (Print) , 28(3), 2012, pp. 529-560
In this paper, we establish a general solution and the generalized Hyers-Ulam-Rassias stability of the following general mixed additive-cubic functional equation f(kx+y)+f(kx.y)=kf(x+y)+kf(x.y)+2f(kx).2kf(x) in the quasi-Banach spaces