Sathikarnmanee, A., and T. Sathitkarnmanee. “Postoperative Oxygen Saturation in Patients Receiving Spinal Anesthesia”. Srinagarind Medical Journal, vol. 12, no. 1, Nov. 2013, pp. 34-37, https://li01.tci-thaijo.org/index.php/SRIMEDJ/article/view/13972.