1. Jones, D.: The phoneme: its nature and Use. Cambridge, England, Heffer (1950)
2. Denes, P.B.: On the statistics of spoken English. J. Acoust. Soc. Am. 35(6), 892–904 (1963)
3. Clements, G.N.: Place of articulation in consonants and vowels: a unified theory. Work. Pap. Cornell Phon. Lab. 5, 77–123 (1991)
4. Rabiner, L. R., Juang, B. H.: Fundamentals of speech recognition. Tsinghua University Press (1999)
5. Hogg, R.M.: Phonology and morphology. Camb. Hist. Engl. Lang. 1, 67–167 (1992)