Sakamoto, Taro
The International Society for Educational Information, 1984.
Buku Teks
Aston, W.G.
Charles E. Tutle, 1981
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Halliday, Jon
Pantheon Books, 1975
Buku Teks
Frellesvig, Bjark
Cambridge University Press, 2010
Buku Teks
Cambridge University Press, 2016
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