Avinash R, Singh PK. Comparative study of intrathecal fentanyl, tramadol, clonidine mixed with bupivacaine for peri and post operative pain relief in lower limb and lower abdominal surgery. Int J Res Med Sci [Internet]. 2019 Dec. 25 [cited 2025 May 16];8(1):140-6. Available from: https://www.msjonline.org/index.php/ijrms/article/view/7208