Shafa, A. et al. 2018. Comparison of pre-emptive analgesic effect of rectal ketamine and caudal bupivacaine in pediatric lower abdominal surgery. Iranian Journal of Pediatric Surgery. 4, 2 (Dec. 2018), 61–70. DOI:https://doi.org/10.22037/irjps.v4i2.22280.