Griffith, Ernest
Frederick A. Praeger, 1954
Buku Teks
Henderson, H. James, author
McGraw-Hill, 1974
Buku Teks
Mezey, Michael L.
Westview Press, 1989
Buku Teks
Matthews, Donald R.
The University of North Carolina Press, 1960
Buku Teks
Baker, Ross K., author
Free Press, 1980
Buku Teks