MacDonald, Austin F., author
Thomas Y. Crowell, 1949
Buku Teks
Millett, John D., author
McGraw-Hill, 1959
Buku Teks
MacCorkle, Stuart A.
D.C. Heath and Company, 1948
Buku Teks
World Bank, 2002
Buku Teks
Dawson, Robert MacGregor
Vancouver The Copp Clark Publshing Co. 1957,
Buku Teks