Oceana Publications, 1958
Buku Teks
Fisher, Louis, author
McGraw-Hill, 1988
Buku Teks
American Enterprise Institute for Public Policy Research, 1987
Buku Teks
Schawartz, Bernard, author
At The University Press, 1955
Buku Teks
Strong, Frank R., author
Dennis & Co., 1950
Buku Teks