Huges, Helen
Johns Hopkins Univesity Press , 1973
Buku Teks
United Nations, 1964
Buku Teks
Malaysian Association for American Studies, 1988.
Buku Teks
Dietrich, Ethel B.
Henry Holt and Company, 1940
Buku Teks
Department of Economic Affairs, 1953
Buku Teks