Organization for Economic Co-operation and Development , 1972
Buku Teks
Departemen Pendidikan dan Kebudayaan, 1980
Buku Teks
Center for International Higher Education Boston Collage,
Majalah, Jurnal, Buletin
Metcalfe, Scoot Amy
Information Science Publishing, 2006
Buku Teks
Her Majesty's Stationery Office, 1987
Buku Teks