Kuno, Susumu: The Structure of the Japanese Language, 1973. MIT Press.
Miller, Roy A: The Japanese Language, 1967. Univ. of Chicago Press.
Shibatani, Masayoshi: The Languages of Japan, 1990. Cambridge University Press.
Takeuchi, Lone: The structure and history of Japanese: from Yamatokotoba to Nihongo, 1999. Longman.
Tsujimura, Natsuko: An Introduction to Japanese Linguistics, 1996. Blackwell Publishers.
In Japanese:
Okutsu, Kei'ichir?: 'Boku wa unagi da' no bunp?: da to no, 2nd edition, 1993. Kurosio Publishers. pp. 7 - 66.
Sat?, Ry?ichi: Okuni-kotoba o shiru: h?gen no chizuch?, 2002. Shogakukan. 'CD "Okuni-kotoba de kiku Momotar?" kaisetsu', pp.1-7 (from the end).
'H?gen no kiso-chishiki', pp. 330-365.