Puapermpoonsiri, P., and R. Eua-apithorn. “Comparison of Nasal Mucociliary Clearance Time with Saccharin Clearance Test of Volunteers in Bangkok and Chiangrai Province: a Pilot Study”. Vajira Medical Journal : Journal of Urban Medicine, vol. 54, no. 3, Sept. 2011, pp. 261-5, https://he02.tci-thaijo.org/index.php/VMED/article/view/455.