Howard, Marshall C.
Englewood Clifts, 1983
Buku Teks
The Foundation Press, Inc., 1975
Buku Teks
Garvey, George E.
Greenwood Press, 1990
Buku Teks
Anderson, Ronald A.
South-Western Publishing Company, 1950
Buku Teks
Barnes, A. James
Irwin, 2000
Buku Teks