The notion of stability of functional equations of several variables in the sense used here had its origins more than half a century ago when S. Ulam posed the

No books dealing with a comprehensive illustration of the fast developing field of nonlinear analysis had been published for the mathematicians interested in th

The notion of stability of functional equations of several variables in the sense used here had its origins more than half a century ago when S. Ulam posed the

The theory of hypergroups is a rapidly developing area of mathematics due to its diverse applications in different areas like probability, harmonic analysis, et

This treatise deals with modern theory of functional equations in several variables and their applications to mathematics, information theory, and the natural,