Kaneez Ume Farwa, Waseema Afzal, Shumaila Ali Rai, Taha Malik, Hafiz Haseeb Ahsan, Fatima Skina. “Comparison of Continuous Infusion of Intravenous Tramadol and Fentanyl on Postoperative Analgesia in Cardiac Surgery”. Pakistan Journal of Medical & Health Sciences, vol. 16, no. 10, Dec. 2022, p. 268, doi:10.53350/pjmhs221610268.