M. Arunkumar, John M. Rassias, S. Murthy, and M. Arulselvan. “Stability of a 2 - Variable AC - Mixed Type Functional Equation in Paranormed Spaces: Direct and Fixed Point Methods”. International Journal of Mathematics And Its Applications, vol. 4, no. 4 (Special Issue), Dec. 2016, pp. 43-58, http://ijmaa.in/index.php/ijmaa/article/view/1419.