Buckley, Roger, author
Cambridge University Press, 1990
Buku Teks
Taeuber, Irene B., author
Princeton University Press, 1958
Buku Teks
International Society for Educational Information, 1989
Buku Teks
[date of publication not identified]
Buku Teks
Forbis, William H.
Charles E.Tuttle, 1981
Buku Teks