Pattira Thanomnark และ Parichart Phootirat. (2014) The acquisition of /r/-/I/ contrast by northern Thai speaking learners. Kasetsart University:ม.ป.ท.Pattira Thanomnark และ Parichart Phootirat. 2014. The acquisition of /r/-/I/ contrast by northern Thai speaking learners. ม.ป.ท.:Kasetsart University;Pattira Thanomnark และ Parichart Phootirat. The acquisition of /r/-/I/ contrast by northern Thai speaking learners. ม.ป.ท.:Kasetsart University, 2014. Print.