Houghton, John W.
Westview Press , 1991
Buku Teks
Golinski, Jan, author
Cambridge University Press , 1992
Buku Teks
Guy, Josephine M, author
Harvester Wheatshef, 1991
Buku Teks
Thomas, David, author
Penguin Books, 1963
Buku Teks
Franta, Andrew, author
Cambridge University Press, 2009
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