Bibi Sarah Pandhiani, Riaz Hussain Shah, Khalil Ahmed Sanghro, Bakht Ali Siyal, Gordhan, Aijaz Ahmed Laghari. Levels of Serum Vitamin D Among Patients of Chronic Obstructive Pulmonary Disease and Its Association With Severity: A Case Control Study. Annals of RSCB 2021, 25, 1837-1845.