Bollens, John C.
Harper and Row, 1970
Buku Teks
Basic Books , 1963
Buku Teks
Marshall, Dale Rogers
Resorces for the future, 1972
Buku Teks
Gilham, Oliver
Islan Press, 2002
Buku Teks
edited by Edwin S. Mills and John F. McDonald ; Mary L. McLean, associate editor
Transaction Publishers, 1992
Buku Teks