Dobb, Maurice, author
International Publishers, 1947
Buku Teks
Frederick, William C., 1925-, author
McGraw-Hill, 1988
Buku Teks
Merton, Robert K., author
Harcourt Brace Jovanovich, 1971
Buku Teks
Hobson, John A.
George Allen and Unwin, 1954
Buku Teks
Department of Commerce , 1980
Buku Teks