[1] Kannappan Pl. Functional Equations and Inequalities with Applications. New York: Springer, 2009
[2] Sahoo P K, Kannappan Pl. Introduction to Functional Equations. Boca Raton: CRC Press, 2011
[3] Ciepliński K. On the generalized Hyers-Ulam stability of multi-quadratic mappings. Comput Math Appl, 2011, 62(9): 3418-3426
[4] Ji P, Qi W, Zhan X. Generalized stability of multi-quadratic mappings. J Math Res Appl, 2014, 34(2): 209-215
[5] Zhao X, Yang X, Pang C T. Solution and stability of the multiquadratic functional equation. Abstr Appl Anal, 2013, Art ID 415053
[6] Brillouët-Belluot N, Brzd?k J, Ciepliński K. On some recent developments in Ulam's type stability. Abstr Appl Anal, 2012, Art ID 716936
[7] Jung S M. Hyers-Ulam-Rassias Stability of Functional Equations in Nonlinear Analysis. New York: Springer, 2011
[8] Azadi Kenary H, Zohdi A R, Eshaghi Gordji M. Fixed points and stability for quartic mappings in β-normed left Banach modules on Banach algebras. Acta Mathematica Scientia, 2013, 33B(4): 1113-1118
[9] Wang Z. A fixed point approach to the stability of a generalized Apollonius type quadratic functional equation. Acta Mathematica Scientia, 2011, 31B(4): 1553-1560
[10] Xu T Z. Approximate multi-Jensen, multi-Euler-Lagrange additive and quadratic mappings in n-Banach spaces. Abstr Appl Anal, 2013, Art ID 648709
[11] Bae J H, Park W G. On a bi-quadratic functional equation and its stability. Nonlinear Anal, 2005, 62(4): 643-654
[12] Brzd?k J, Ciepliński K. Remarks on the Hyers-Ulam stability of some systems of functional equations. Appl Math Comput, 2012, 219(8): 4096-4105
[13] Cho Y J, Park C, Eshaghi Gordji M. Approximate additive and quadratic mappings in 2-Banach spaces and related topics. Int J Nonlinear Anal Appl, 2012, 3(2): 75-81
[14] Moslehian M S, Rassias Th M. Stability of functional equations in non-Archimedean spaces. Appl Anal Discrete Math, 2007, 1(2): 325-334
[15] Chung S C, Park W G. Hyers-Ulam stability of functional equations in 2-Banach spaces. Int J Math Anal (Ruse), 2012, 6(17/20): 951-961
[16] Ciepliński K, Xu T Z. Approximate multi-Jensen and multi-quadratic mappings in 2-Banach spaces. Carpathian J Math, 2013, 29(2): 159-166
[17] Park W G. Approximate additive mappings in 2-Banach spaces and related topics. J Math Anal Appl, 2011, 376(1): 193-202
[18] Khrennikov A. Non-Archimedean Analysis: Quantum Paradoxes, Dynamical Systems and Biological Models. Dordrecht: Kluwer Academic Publishers, 1997
[19] Azadi Kenary H. Approximation of a Cauchy-Jensen additive functional equation in non-Archimedean normed spaces. Acta Mathematica Scientia, 2012, 32B(6): 2247-2258
[20] Freese R W, Cho Y J. Geometry of Linear 2-normed Spaces. Hauppauge, NY: Nova Science Publishers, Inc, 2001
[21] Gao J. On the stability of the linear mapping in 2-normed spaces. Nonlinear Funct Anal Appl, 2009, 14(5): 801-807