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Hammod Incorproted, 1986
Buku Referensi
Garden City Books, [date of publication not identified]
Buku Referensi
Rand Mcnally, 1967
Buku Referensi
Lewis, Richard J., author
Wiley-Interscience, 2002
Buku Referensi
editors, Gerald P. Koocher, John C. Norcross, Sam S. Hill, III
Oxford University Press, 2005
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