Butt, David
Oxford University Press, 1990
Buku Teks
Klippel, Friederike, author
Cambridge University Press , 1993
Buku Teks
lu Bisong
Beijing : Beijing Daxue, 2008
Buku Referensi
Cambridge University Press, 2010
eBooks
Brezina, Vaclav, 1979-, author
Cambridge University Press, 2018
Buku Teks