G. Britto Antony Xavier, M. Meganathan, and E. L. Gohila. “Finite Fourier Series Decomposition of Functions (Signals) of Three Variables”. International Journal of Mathematics And Its Applications, vol. 6, no. 1 (Special Issue), May 2018, pp. 33-39, http://ijmaa.in/index.php/ijmaa/article/view/1392.