Levi, Werner
The University of Minnesota Press, 1953
Buku Teks
Kim, Samuel S., 1935-, author
Westview Press, 1984
Buku Teks
Bennett, A. LeRoy, author
Prentice-Hall, 1977
Buku Teks
March, James G., author
Wiley, 1950
Buku Teks
Luard, Evan
Oxford University Press , 1964
Buku Teks