Latif, Rifat, et al. “Nalbuphine and Tramadol in the Treatment of Post Spinal Anesthesia Shivering: A Randomized Control Study”. Pakistan Journal of Physiology, vol. 16, no. 4, Dec. 2020, pp. 17-20, https://pjp.pps.org.pk/index.php/PJP/article/view/1263.