[1]
Fan Y., Ji M., Zang L., Wang W., Yin Q., Xu J. and Yang J. 2011. Comparison of epidural tramadol-ropivacaine and fentanyl-ropivacaine for labor analgesia: A prospective randomized study. Upsala Journal of Medical Sciences. 116, 4 (Nov. 2011), 252–257. DOI:https://doi.org/10.3109/03009734.2011.601532.