C.H., M. and G., L.N. 2017. Effects of fentanyl on isobaric ropivacaine in subarachnoid anaesthesia for lower abdominal and lower extremity surgeries. International Journal of Research in Medical Sciences. 4, 7 (Jan. 2017), 2850–2855. DOI:https://doi.org/10.18203/2320-6012.ijrms20161963.