Murad, Rafat, et al. “Comparison of Serum Levels of Vitamin D and Vitamin D-Binding Protein in Normal, Osteopenic and Osteoporotic Postmenopausal Women: Vitamin D and Vitamin D-Binding Proteins in Post Menopausal Females”. Pakistan Journal of Medical Sciences, vol. 35, no. 2, Mar. 2019, doi:10.12669/pjms.35.2.714.