et. al, D. D. “Synthesis and Spectral Evaluation of Zeolite and Nanotubes of Silica: The Rich Constituents of Rice Husk Ash.”. International Journal of Advanced Science and Technology, Vol. 29, no. 2, Jan. 2020, pp. 3056 -4, http://sersc.org/journals/index.php/IJAST/article/view/4367.