Al Maruf, Abdullah, et al. “Epidural Administration of Ketamine or Fentanyl With Bupivacaine for Postoperative Analgesia – A Comparative Study”. Journal of the Bangladesh Society of Anaesthesiologists, vol. 22, no. 1, Feb. 2014, pp. 21-25, doi:10.3329/jbsa.v22i1.18097.