Abdul Ghani Waseem, Kaleem Ullah Toori, Mohammad Iqbal, Asim Zulfiqar, Sharif-uz-Zaman. “Effect of Job Environment on Pulmonary Functions of Railway Employees”. Journal of Rawalpindi Medical College, vol. 12, no. 2, Dec. 2009, https://journalrmc.com/index.php/JRMC/article/view/753.