Dr. Jaimin A Mansuriya, et al. “RELATIONSHIP BETWEEN SEVERE VITAMIN D DEFICIENCY AND FREQUENCY OF COPD EXACERBATIONS: A RETROSPECTIVE COHORT STUDY AT A TERTIARY CARE CENTER IN NORTH INDIA”. Journal of Population Therapeutics and Clinical Pharmacology, vol. 32, no. 9, Oct. 2025, pp. 1582-90, https://doi.org/10.53555/sp8cyq47.