DJVU PDF Hong, N.Q. 1992, "Neutral vowels in languages of different types", in The Third International Symposium on Language and Linguistics, Bangkok, Thailand, pp. 94-97. Chulalongkorn University. cite.
DJVU PDF Dhananjayananda, P. 1992, "The emergence of length distinction of mid-front vowels /e-ee/ in Thai", in The Third International Symposium on Language and Linguistics, Bangkok, Thailand, pp. 1294-1304. Chulalongkorn University. cite.