Shah, H. A., J. S. B., and M. Bhavsar. “A Comparative Study of Oral Tapentadol With Thoracic Epidural Analgesia Versus Intravenous Tramadol and Paracetamol Combination for Postoperative Analgesia in off Pump CABG”. International Journal of Basic & Clinical Pharmacology, vol. 2, no. 6, Feb. 2017, pp. 723-7, https://www.ijbcp.com/index.php/ijbcp/article/view/1356.