Hiroshi, Watanabe
I-House Press, 2012
Buku Teks
Tzouvala, Ntina
Cambridge University Press, 2020
eBooks
Cammack, Paul Anthony
Leicester University Press, 1997
Buku Teks
Sakamoto, Taro
The International Society for Educational Information Press, Inc., 1975
Buku Teks
Aston, W.G.
Charles E. Tutle, 1981
Buku Teks