Seth, A., and B. K. Kalra. “Prevalence of Vitamin D Deficiency Among Old Patients Visiting OPD of a Tertiary Care Teaching Hospital”. International Archives of BioMedical and Clinical Research, Vol. 5, no. 4, Dec. 2019, pp. GM17-GM19, doi:10.21276/iabcr.2019.5.4.19.