Deo, G P, S K Shrestha, and I N Shrestha. 2017. “Epidural Butorphanol for Post Operative Analgesia in Lower Limb Surgeries: A Comparative Study With Epidural Tramadol”. Journal of Chitwan Medical College 6 (3):26-32. https://nepjol.info/index.php/JCMC/article/view/16696.