Beveridge, Charles E., author
Universe, 1998
Buku Teks
Rudolph, Frederick
Knopf , 1962
Buku Teks
Friedman, Lawrence M., 1930-, author
W.W. Norton, 1984
Buku Teks
Downs, Frederick
W.W. Norton & Company, 1991
Buku Teks
Hoffman, Frederick J.
The Free Press, 1962
Buku Teks