Takeshi, Nakagawa
The International House of Japan, 2005
Buku Referensi
Carver, Norman F.
Shokokusha, 1955
Buku Teks
Howard, Darlene V.
Macmillan, 1983
Buku Teks
Frellesvig, Bjark
Cambridge University Press, 2010
Buku Teks SO
Susumo, Ohno
Kokusai Bunka Shinkoka, 1970
Buku Teks SO