A. P. Siregar, Rukiah Chodilawati, and Mgs. Irsan Saleh, “The Effect of Giving Vitamin D Supplements on Improving Ejection Fraction in Heart Failure Patients at Dr. Mohammad Hoesin General Hospital, Palembang, Indonesia”, Bioscmed, vol. 7, no. 10, pp. 3628-3636, Sep. 2023.