M. Arunkumar, S. Karthikeyan, S. Hemalatha. Stability of 2-variable additive-quadratic-cubic-quartic functional equation using fixed point method. Malaya J. Mat. [Internet]. 2017 Apr. 1 [cited 2024 Nov. 21];5(02):241-64. Available from: https://www.malayajournal.org/index.php/mjm/article/view/591