Javed, T., Ahad, B., Singh, P. and Ahmad, R. 2017. A prospective randomized study to compare tramadol and morphine for postoperative analgesia in spine surgeries using intravenous patient controlled analgesia. International Journal of Research in Medical Sciences. 5, 8 (Jul. 2017), 3350–3354. DOI:https://doi.org/10.18203/2320-6012.ijrms20173140.