Wanwipa Panyajirawut และ Preeyachat Uttamayodhin. (2009) Factors influencing confidence in speaking English :. Thammasat University:ม.ป.ท.Wanwipa Panyajirawut และ Preeyachat Uttamayodhin. 2009. Factors influencing confidence in speaking English :. ม.ป.ท.:Thammasat University;Wanwipa Panyajirawut และ Preeyachat Uttamayodhin. Factors influencing confidence in speaking English :. ม.ป.ท.:Thammasat University, 2009. Print.