edited by W. Arthur Cullman and Harry R. Knudson
Prentice-Hall, 1972
Buku Teks
Litvak, Isaiah A., author
McGraw-Hill Ryerson, 1984
Buku Teks
Vernon, Raymond, author
Prentice-Hall, 1996
Buku Teks
Bouckaert, Geert, author
Palgrave Macmillan, 2010
Buku Teks
Lewis, Jordan D., author
Free Press, 1990
Buku Teks