H. B. Gupta and S. N. Amilkanthwar, “A prospective, comparative, observational study of quality of spinal anaesthesia with 0.5% and 0.75% plain isobaric ropivacaine in lower abdomen and lower limb surgeries”, Int J Res Med Sci, vol. 4, no. 8, pp. 3134–3140, Jan. 2017.