Raheja, A., Agarwal, K., Pachori, R., & Gandhi, G. (2019). Tramadol versus placebo for labor analgesia in low risk women: a randomized controlled trial. International Journal of Reproduction, Contraception, Obstetrics and Gynecology, 9(1), 342–347. https://doi.org/10.18203/2320-1770.ijrcog20196045