Bisht, S., and D. Rashmi. “Comparison of Intrathecal Fentanyl and Nalbuphine: A Prospective Randomized Controlled Study in Patients Undergoing Total Abdominal Hysterectomy”. Anaesthesia, Pain & Intensive Care, Jan. 2019, pp. 194-8, https://mail.apicareonline.com/index.php/APIC/article/view/110.