Singh, P., A. Hussain, R. B, M. Mishal, and H. Jingar. “A Comparative Study of Efficacy of Analgesiaand Anaesthesia Between Intrathecal ButorphanolAndFentanyl With Bupivacaine 0.5% Heavy for Lower Limb Orthopedic Surgery: A Prospective Randomized Study”. International Journal of Health and Clinical Research, vol. 4, no. 3, Feb. 2021, pp. 56-60, https://ijhcr.com/index.php/ijhcr/article/view/871.