Arunakul, P. ., and T. . Ruangprach. “Efficacy and Safety of Intrathecal Morphine in Patients Underwent Foot and Ankle Surgery; A Retrospective Study”. Asian Medical Journal and Alternative Medicine, vol. 22, no. -, Aug. 2022, p. S123, https://asianmedjam.com/index.php/amjam/article/view/1302.