Khamka, A., and A. Santeerapharp. “The efficacy of normal saline compared with standard lubricant in nasal endoscope by flexible laryngoscope”. Journal of Medicine and Health Sciences, vol. 26, no. 1, Apr. 2019, pp. 1-9, https://he01.tci-thaijo.org/index.php/jmhs/article/view/185685.