Ahmed, Shaheda, et al. “A Study on Vitamin D Levels in Patients Attended at OPD of A Tertiary Care Hospital of Chattogram”. Chattagram Maa-O-Shishu Hospital Medical College Journal, vol. 18, no. 2, June 2020, pp. 37-40, doi:10.3329/cmoshmcj.v18i2.47771.