Benjamas Khamsakul. (1998) The attitude of So (Thavung) ethnic group toward their own language and its use : case study of Nong Waeng village, Pathumwapi subdistricts, Song Dao district, Sakon Nakhorn province. Mahidol University,:ม.ป.ท.Benjamas Khamsakul. 1998. The attitude of So (Thavung) ethnic group toward their own language and its use : case study of Nong Waeng village, Pathumwapi subdistricts, Song Dao district, Sakon Nakhorn province. ม.ป.ท.:Mahidol University,;Benjamas Khamsakul. The attitude of So (Thavung) ethnic group toward their own language and its use : case study of Nong Waeng village, Pathumwapi subdistricts, Song Dao district, Sakon Nakhorn province. ม.ป.ท.:Mahidol University, 1998. Print.