Zhang, C.- hong, J.- hua Liu, J.- qing Zhao, Z.- hua Zhang, and X. Gu. “Clinical Study on the Effect of Bi-Level Positive Airway Pressure Therapy on COPD Complicated With Anxiety and Depression”. Pakistan Journal of Medical Sciences, Vol. 39, no. 5, Aug. 2023, doi:10.12669/pjms.39.5.7259.