Downes, John
barron's, 2006
Buku Teks
Hildreth, Sandra S.
Dearborn Financial Publishing, 1988
Buku Referensi
Jordan, John E.
Harper & Row, Publishers, 1965
Buku Teks
Oxford University Press, 1993
Buku Referensi
Damisch, Hubert
MIT Press, 2000
Buku Teks