Organisation for Economic Co-operation and Development, 1974
Buku Teks
Unesco , 1968
Buku Teks
Faludi, Andreas, author
Pergamon Press, 1978
Buku Teks
Beeby, C. E., author
New Zealand Council for Educational Research, 1979
Buku Teks
Kaufman, Roger A.
Prentice-Hall, 1972
Buku Teks