[1] SUN Yong-Sheng, WANGH He-ping. Representation and approximation of multivariate periodic functions with bounded mixed moduci of smoothness [J]. Proceeding of the Institute of Mathematics 1997, 219. [2] Pinkus A. N-Widths in apprixi mation theory [M]. New York: Springer-Verlag 1985. [3] NIKOL′SKII SM. Approximation of functions of several variables and imbedding theorems [M]. New york:Springer-Verlag 1975. |