Saifon Sa-adkaew และ Sasi Jungsatitkul. (2011) The relationship between aristotle's rhetoric and tense choice in CEO letters /. Khon Kaen University,:ม.ป.ท.Saifon Sa-adkaew และ Sasi Jungsatitkul. 2011. The relationship between aristotle's rhetoric and tense choice in CEO letters /. ม.ป.ท.:Khon Kaen University,;Saifon Sa-adkaew และ Sasi Jungsatitkul. The relationship between aristotle's rhetoric and tense choice in CEO letters /. ม.ป.ท.:Khon Kaen University, 2011. Print.