Robinson, Marshall A., author
Brookings Institution, 1955
Buku Teks
Schiller, Bradley R., author
Random House of Canada, 1980
Buku Teks
Schiller, Bradley R., author
McGraw-Hill , 1997
Buku Teks
Daughterty, Caroll R., author
Houghton Mifflin, 1950
Buku Teks
McKenzie, Richard B., author
McGraw-Hill, 1978
Buku Teks