วิวัฒน์ภิญโญ ศ, ลีลาเกียรติสกุล ว. Improvement on the anti-VoIP spam mechanisms using Reverse Turing Test. JIST [Internet]. 2011 Dec. 30 [cited 2024 May 4];2(2):45-5. Available from: https://ph02.tci-thaijo.org/index.php/JIST/article/view/135187