Sreekumar, A., and Kiran Kumar. “Using a Peak Flow Meter to Assess Severity of Exacerbation in Patients Suffering from Chronic Obstructive Pulmonary Disease: A Prospective Observational Study”. International Journal of Research in Medical Sciences, vol. 11, no. 5, Apr. 2023, pp. 1526-30, doi:10.18203/2320-6012.ijrms20231036.