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Clarendon Press, 2005
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Aveling, Harry, author
2006
Artikel Jurnal
Harrison, John B.
Alfred A. Knopf, 1966
Buku Teks
Nisbet, Robert A., author
Oxford University Press, 1970
Buku Teks
Harrison, John B.
Alfred A. Knopf, 1969
Buku Teks