Khanam, R.A. et al. 2013. A Controlled Trial of Noninvasive Positive Pressure Ventilation (NIPPV) in Patients of COPD with Respiratory Failure. Bangladesh Critical Care Journal. 1, 2 (Dec. 2013), 86–92. DOI:https://doi.org/10.3329/bccj.v1i2.17201.