Ly Van An. “Generalized Hyers-Ulam Type Stability of the $2k$-Variables Quadratic $\beta$-Functional Inequalities And Function in $\gamma$-Homogeneous Normed Space”. International Journal of Mathematics And Its Applications, vol. 9, no. 3, Sept. 2021, pp. 81-93, http://ijmaa.in/index.php/ijmaa/article/view/47.