Choudhary, A., S. Maheshwari, N. Paliwal, S. Ujwal, and G. Singariya. “Comparative Study of Fentanyl Versus Tramadol As Adjuvant With Low Dose Local Anaesthetic Ropivacaine (0.1%) for Epidural Labour Analgesia”. International Journal of Research in Medical Sciences, vol. 8, no. 9, Aug. 2020, pp. 3309-14, doi:10.18203/2320-6012.ijrms20203684.