Siregar, Andi Putra, et al. “The Effect of Giving Vitamin D Supplements on Improving Ejection Fraction in Heart Failure Patients at Dr. Mohammad Hoesin General Hospital, Palembang, Indonesia”. Bioscientia Medicina : Journal of Biomedicine and Translational Research, vol. 7, no. 10, Sept. 2023, pp. 3628-36, https://doi.org/10.37275/bsm.v7i10.869.