Zhang*, Xiang-Lin, et al. “La,N-Codoped TiO2 Visible-Light Responsive Photocatalysts Prepared by Hydrolysis Precipitation Method”. Asian Journal of Chemistry, vol. 23, no. 5, Jan. 2011, pp. 2343-6, https://asianpubs.org/index.php/ajchem/article/view/10387.