N. Pathak, T. Tiwari, S. Singh, Y. K. Manik, V. K. Dhama, and S. Dahiya, “A clinical comparative study of ropivacaine versus ropivacaine with fentanyl by continuous epidural infusion for post-operative analgesia and ambulation in patients undergoing major gynecological surgery”, Int J Reprod Contracept Obstet Gynecol, vol. 7, no. 4, pp. 1561–1566, Mar. 2018.