Nakagawa, K., 		Yamada, K., 		Tsurue, T., 		Takeda, S., 		Ishizaki, K., 		Quialao, T., 		Balais, W., 		Herrera, A., 		Pugal, D., 		Bion, H., 		Magpantay, C., 		Abarquez, F., 		Alcoba, E., AND 		Vinluan Jr., F..
" Highly Active Absorbent for SO₂ Removal Prepared from Coal Ash (Part 1)" <em>Philippine Engineering Journal</em> [Online], Volume 19 Number 1 (26 August 2021)