Wongswadiwat, M., S. Thienthong, W. Krisanaprakornkit, S. Pongjanyakul, and W. Taesiri. “Survey of Postoperative Pain Management Orders at Srinagarind Hospital”. Srinagarind Medical Journal, vol. 17, no. 1, Nov. 2013, pp. 20-25, https://li01.tci-thaijo.org/index.php/SRIMEDJ/article/view/14387.