Nguyen, Hien, Qui Thi Le, Dai Xuan Ngo, Hanh Nguyen, Chinh Dang Huynh, & Lin Viet Dao. " Preparation and investigation of optical properties of ZnO: Co powders." VNU Journal of Science: Mathematics - Physics [Online], 20.3AP (2004): n. pag. Web. 16 May. 2024