Kolutek Ay, B., E. Berk, A. Demirel, and V. Nacitarhan. “The Correlation Between Neuropathic Pain Incidence and Vitamin D Levels in Patients With Chronic Low Back Pain”. Annals of Medical Research, vol. 26, no. 12, May 2021, pp. 3037-41, http://www.annalsmedres.org/index.php/aomr/article/view/1869.