Hang, Phung, 		Ke, Nguyen, 		Phuong, Duong, AND 		Hung, Le.
" Enhancing the photocatalytic activity under visible light of chromium doped TiO2 thin film prepared by sol-gel method" <em>VNU Journal of Science: Mathematics - Physics</em> [Online], Volume 27 Number 4 (15 December 2011)