Ramage, Douglas E.
Routledge , 1997
Buku Teks
Arblaster, Anthony
Open University Press, 1987
Buku Teks
Oxford University Press, 1995
Buku Teks
Schulz, Ernest B
[publisher not identified], 1956
Buku Teks
Shi Biqiu
China Renmin University Press, 2015
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