Chase, Eugene P.
McGraw-Hill Book , 1950
Buku Teks
UNESCO, 1962
Buku Teks
United Nations, 1992
Buku Referensi
Goodrich, Leland M., author
Thomas Y. Crowell, 1961
Buku Teks
United Nations
Kantor Penerangan PBB, [date of publication not identified]
Buku Teks