↑ Nordhoff, Sebastian; Hammarström, Harald; Forkel, Robert; Haspelmath, Martin biên tập (2013). “Kha Phong”. Glottolog. Leipzig: Max Planck Institute for Evolutionary Anthropology. Đã bỏ qua tham số không rõ |chapterurl= (trợ giúp)
↑ Chamberlain, J.R. 1998, "The origin of Sek: implications for Tai and Vietnamese history", in The International Conference on Tai Studies, ed. S. Burusphat, Bangkok, Thailand, pp. 97-128. Institute of Language and Culture for Rural Development, Mahidol University.
