S. Sakhaei, H. E. Sadagheyani, S. Zinalpoor, A. K. Markani, and H. Motaarefi, “The Impact of Pursed-lips Breathing Maneuver on Cardiac, Respiratory, and Oxygenation Parameters in COPD Patients”, Open Access Maced J Med Sci, vol. 6, no. 10, pp. 1851–1856, Oct. 2018.