Singh, Jeevan, et al. “Comparison of Ketamine, Fentanyl and Clonidine As an Adjuvant During Bupivacaine Caudal Anaesthesia in Paediatric Patients”. Kathmandu University Medical Journal, vol. 10, no. 3, Apr. 2013, pp. 25-29, doi:10.3126/kumj.v10i3.8013.