Edmondson, J. A., & Solnit, D. B. (1988). Comparative Kadai: linguistic studies beyond Tai. Summer Institute of Linguistics publications in linguistics, no. 86. [Arlington, Tex.]: Summer Institute of Linguistics. ISBN0-88312-066-6
Li, Jinfang [李锦芳]. 2006. Studies on endangered languages in the Southwest China [西南地区濒危语言调查研究]. Beijing: Minzu University.
Ostapirat, Weera. (2000). "Proto-Kra." Linguistics of the Tibeto-Burman Area23 (1): 1-251.