N.Y. AMA , 1982
Buku Teks
Williams, David, author
Sweet & Makwell, 2000
Buku Teks
Crestol, Jack
Dow Joner-Irwin, 1983
Buku Teks
Crumbley, D Larry
Barron's Educational Series, 1994
Buku Teks
McDonald, Stephen L.
The Brookings Institution , 1963
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