S. Au–pree, P. Narakaew, S. Thungprasert, T. Promanan, A. Chaisena, and S. Narakaew, “Enhanced Photocatalytic Activity of C-doped TiO2 under Visible Light Irradiation: A Comparison of Corn Starch, Honey, and Polyethylene Glycol as a Carbon Sources”, Eng. J., vol. 25, no. 1, pp. 53–68, Jan. 2021, doi: 10.4186/ej.2021.25.1.53.