Stern, Robert L.
The Bureau of National Affairs, 1969
Buku Teks
Abraham, Henry J., author
Oxford University Press, 1988
Buku Teks
Pacelle, Richard L., Jr.
Westview Press, 1991
Buku Teks
Talbot, Phillips, author
Harper and Brothers, 1958
Buku Teks
Seligman, Eustace, author
New York University Press, 1956.
Buku Teks