Thi Xuan, Bui, Tien Thanh, Ngo, AND Khanh Linh, To. " Analysis of Direct Treatment Cost for Exacerbation of Chronic Obstructive Pulmonary Disease in E Hospital from October 2019 to March 2020" VNU Journal of Science: Medical and Pharmaceutical Sciences [Online], Volume 36 Number 2 (25 June 2020)