Department of Public Information. United Nations
Department of Public Information, 2000
Buku Teks
Buku Teks
Charles W. Eliot, edited
P. F. Collier & Son Corporation, 1959 ; 1969
Buku Referensi
Pacey, Arnold, editor
Intermediate Technology , 1980
Buku Teks
Wiggins, Bob
Gower , 2000
Buku Teks