Chongkolwatana, C., C. Metheetrairut, S. Chongvisal, and P. Keskool. “The Sensitivity of Transnasal Biopsy at Random for The Diagnosis of Nasopharyngeal Carcinoma”. Siriraj Medical Journal, vol. 51, no. 4, Apr. 1999, pp. 244-51, https://he02.tci-thaijo.org/index.php/sirirajmedj/article/view/246982.