Chaudhry, Asma, et al. “FREQUENCY AND RISK FACTORS OF FREQUENT EXACERBATIONS OF ASTHMA IN PATIENTS IN A TERTIARY CARE HOSPITAL: A HOSPITAL-BASED COMPARATIVE STUDY: Exacerbations of Asthma in Patients”. Pakistan Armed Forces Medical Journal, vol. 68, no. 2, Apr. 2018, pp. 207-13, https://pafmj.org/PAFMJ/article/view/213.