Kuenzang Norbu และ Pattarasinee Bhattarakosol. (2012) Usefulness determination of text-based CAPTCHA in a group of Developing countries. Chulalongkorn University:ม.ป.ท.Kuenzang Norbu และ Pattarasinee Bhattarakosol. 2012. Usefulness determination of text-based CAPTCHA in a group of Developing countries. ม.ป.ท.:Chulalongkorn University;Kuenzang Norbu และ Pattarasinee Bhattarakosol. Usefulness determination of text-based CAPTCHA in a group of Developing countries. ม.ป.ท.:Chulalongkorn University, 2012. Print.