Abdul-Razaq, Mohammad Yahya, et al. “Etiologies of Chronic Cough in Adult Patients: Is It Hard to Be Diagnosed?”. AL-Kindy College Medical Journal, vol. 7, no. 2, Dec. 2011, pp. 45-50, https://jkmc.uobaghdad.edu.iq/index.php/MEDICAL/article/view/638.