Artikel Jurnal
Gwartney, James D., author
Harcourt Brace Jovanovich, 1990
Buku Teks
Gwartney, James D., author
The Reyden Press, 2000
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Gwartney, James D., author
Dryden Press, 1995
Buku Teks
Gwartney, James D., author
Harcourt Brace Jovanovich, 1987
Buku Teks