Thi, Ngoc, Oanh Hoang, and Hien Thi To. “Air Quality Improvement Estimation Using Contingent Valuation Method in HoChiMinh City”. VNUHCM Journal of Science and Technology Development 17, no. 4 (December 31, 2014): 5-12. Accessed April 24, 2025. http://stdj.scienceandtechnology.com.vn/index.php/stdj/article/view/1533.