1. Nasal Vowel Evolution in Romance
2. Hajek, J. (1991) The Effect of Nasality on Vowel Height: The Allophonic and Phonological Relationship in Romance: A Case Study in Northern Italian. Progress Reports from Oxford Phonetics, 4, 23-28.
3. Matte, E.J. (1982)Histoire Des Modes Phonetiques Du Français. Librairie Droz, Geneva.
4. Rochet, B. (1974) About a Pseudo-Linguistic Universal: That Nasal Vowels Have a Tendency to Lower. Proceedings of the 11th International Congress of Linguists, Vol. 2-3, 727-730.
5. Ruhlen, M. (1973) Nasal Vowels. Working Papers in Language Universals, 12, 1-36.