Deutsch, Babette, author
Funk & Wagnalls, 1957
Buku Referensi
Downes, John, author
barron's, 2006
Buku Teks
Friedman, Jack P., author
Barron's Educational Series, 2007
Buku Referensi
Hildreth, Sandra S., author
Dearborn Financial Publishing, 1988
Buku Referensi
Joel G. Siegel, author
N.Y Barron, 1995
Buku Referensi