Kumar, A., Gupta, K., Gupta, P. K., Rastogi, B., Agrawal, B., & Kalra, P. (2019). Clinical Efficacy of Nalbuphine Versus Tramadol as Analgesic Adjuvant to Fentanyl During Major Abdominal Surgery Performed Under General Anesthesia- A Double Blind Randomized Study. Academia Anesthesiologica International, 4(1), 76-80. https://doi.org/10.21276/aan.2019.4.1.17