Bhavin Mansukhlal Patel. “On the Stability of the Quadratic Functional Equation $f(2x+y) + f(x+2y)$ $= 4f(x+y) + f(x) + f(y)$ in $2$-Banach Space”. International Journal of Mathematics And Its Applications, vol. 13, no. 4, Jan. 2026, pp. 41-53, https://ijmaa.in/index.php/ijmaa/article/view/1631.