“Comparative Study of Flutter Device and Active Cycle of Breathing Technique in Airway Clearance in Subjects With Chronic Obstructive Pulmonary Disease”. Indian Journal of Physiotherapy and Occupational Therapy - An International Journal, vol. 14, no. 3, July 2020, pp. 232-8, https://doi.org/10.37506/ijpot.v14i3.9700.