Manochiopinig, Sriwimon, Apirag Chuangsuwanich, and Sitthichoke Taweepraditpol. 2005. “The Nasoendoscopy Study of Velopharyngeal Closure Patterns in Normal Thai Volunteers”. Siriraj Medical Journal 57 (5):118-21. https://he02.tci-thaijo.org/index.php/sirirajmedj/article/view/245585.