1. Department of Respiratory Medicine, Government Medical College Bhavnagar, Maharaja Krishnakumarsinhji Bhavnagar University, Bhavnagar, India.
2. Department of Community Medicine, Government Medical College Bhavnagar, Maharaja Krishnakumarsinhji Bhavnagar University, Bhavnagar, India.
3. Division of Clinical Epidemiology, ICMR-National Institute of Occupational Health (NIOH), Ahmedabad, India.