Viorst, Milton, author
Chilton Books, 1965
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Phillip R.Trimble
Aspen Law & Business, 1999
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Asia -Pacific Economic Cooperation Secretariat, 1999,
Buku Referensi
Harris, Cyril M., author
W.W. Norton, 1998
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selected by Henry Steele Commager
American Museum of Natural History, 1964
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