Eastwood, Brigitte, Nicola Jepsen, Katie Coulter, Conroy Wong, and Irene Zeng. “Challenges of Undertaking a Clinical Trial Using Bubble-PEP in an Acute Exacerbation of Chronic Obstructive Pulmonary Disease: A Feasibility Study”. New Zealand Journal of Physiotherapy 44, no. 1 (March 1, 2016): 8–16. Accessed September 20, 2024. https://nzjp.otago.ac.nz/nzjp/article/view/122.