Anderson, Vernon E.
The Ronald Press, 1962
Buku Teks
Boyer, Ernest L.
Harper & Row, Publishers, 1983
Buku Teks
Connell, W.F.
Australian Council for Educational Research, 1968
Buku Teks
Gorlewski, Julie A.
Sense, 2012
eBooks
Day, Barbara
Maxwell Macmillan, 1994
Buku Teks