To, Hien, and Hanh Lai. “INVESTIGATION OF THE OZONE POLLUTION LEVEL IN SOME PHOTOCOPY ENTERPRISES AND METHOD OF TREATMENT”. VNUHCM Journal of Science and Technology Development 14, no. 4 (December 30, 2011): 94-100. Accessed June 2, 2025. http://stdj.scienceandtechnology.com.vn/index.php/stdj/article/view/2040.