M. Arunkumar, E. Sathya, S. Karthikeyan, G. Ganapathy, and T. Namachivayam. 2018. “Stability of System of Additive Functional Equations in Various Banach Spaces: Classical Hyers Methods”. Malaya Journal of Matematik 6 (01). India:91-112. https://doi.org/10.26637/MJM0601/0014.