Doan, N. M., C. R. Estrellan, A. Purnomo, A. Gallardo, C. Salim, and H. Hinode. “Characterization and Photocatalytic Activity of Nano-TiO2 Doped With Iron and Niobium for Turquoise Blue Dye Removal”. ASEAN Journal of Chemical Engineering, Vol. 12, no. 1, Dec. 2012, pp. 34-41, https://dev.journal.ugm.ac.id/v3/AJChE/article/view/8120.