[1] ZADEH L A. Fuzzy sets[J]. Inf Control, 1965, 8(3): 338-353. DOI:10.1016/S0019-9958(65)90241-X. [2] ANASTASSIOU G A. Fuzzy mathematics: Approximation theory[M]. Heidelberg: Springer, 2010. [3] GOETSCHEL R, VOXMAN W. Elementary fuzzy calculus[J]. Fuzzy Sets Syst, 1986, 18(1): 31-43. DOI:10.1016/0165-0114(86)90026-6. [4] DEMIRCI K, DIRIK F. Four-dimensional matrix transformation and rate of A-statistical convergence of periodic functions[J]. Math Comput Model, 2010, 52(9/10): 1858-1866. DOI:10.1016/j.mcm.2010.07.015. [5] STOROZˇENKO È A. Approximation of functions of class Hp,0<p≤1[J]. Math USSR-Sb, 1978, 34(4): 527-545. DOI: 10.1070/SM1978v034n04ABEH001228. [6] 陈英伟,王志军.四元数Hardy空间中的slice正则Jackson定理[J].河北大学学报(自然科学版), 2019, 39(3): 230-234. DOI: 10.3969/j.issn.1000 -1565.2019.03.002. [7] ANASTASSIOU G A. Fuzzy approximation by fuzzy convolution type operators[J]. Comput Math Appl, 2004, 48(9): 1369-1386. DOI:10.1016/j.camwa.2004.10.027. [8] TAS E, YURDAKADIM T, ATLIHAN O G. Korovkin type approximation theorems in weighted spaces via power series method[J]. Oper Matrices, 2018, 12(2): 529-535. DOI: 10.7153/oam-2018-12-32. [9] AHIN P O, DIRIK F. A Korovkin-type theorem for double sequences of positive linear operators via power series method[J]. Positivity, 2018, 22(1): 209-218. DOI:10.1007/s11117-017-0508-7. [10] DEVORE R A, LORENTZ G G. Construction approximation[M]. Berlin: Springer-Verlag, 1993. [11] GARNETT J B. Bounded analytic functions[M]. New York: Academic Press, 1981. ( |