Downes, John, author
barron's, 2006
Buku Teks
Downes, John
Barron's Educational Series, 1998
Buku Referensi
Hildreth, Sandra S., author
Dearborn Financial Publishing, 1988
Buku Referensi
Oxford University Press, 1993
Buku Referensi
Goode, Walter, author
Cambridge University Press, 2007
Buku Referensi