Mickelburgh, John
Profesional Books, 1979
Buku Teks
Epstein, David G., author
West Publishing Company, 1976
Buku Teks
editor, Hoyt Gimlin
Congressional Quarterly, 1978
Buku Teks
Goldring, John, author
The Federation Press, 1993
Buku Teks
Ingram, Jefferson L., author
Pearson/Prentice Hall, 2005
Buku Teks