Williams, Numan A., author
South-Western Publicashing, 1984
Buku Teks
Dorfman, Mark S.
Prentice-Hall, 1998
Buku Teks
Williams, Numan A., author
South Western , 1984
Buku Teks
Vaughan, Emmett J., author
John Wiley & Sons, 2001
Buku Teks
Bruce D. Mudget [and others]
Alexander Hamilton Institute, 1962
Buku Teks