Suleman, Amir, Raza Ullah, Hamid Nisar, Shahida Naz, and Rab Nawaz Khan. 2018. “Prevalence of Influenza Vaccination in Chronic Obstructive Pulmonary Disease Patients”. Pakistan Journal of Chest Medicine 24 (2):86-90. http://www.pjcm.net/index.php/pjcm/article/view/519.