Shrestha, SK, et al. “Comparative Study of Hyperbaric Bupivacaine Plus Ketamine Vs Bupivacaine Plus Fentanyl for Spinal Anaesthesia During Caeserean Section”. Kathmandu University Medical Journal, vol. 11, no. 4, Sept. 2015, pp. 287-91, doi:10.3126/kumj.v11i4.12523.