Smith, L. Glenn, author
Allyn and Bacon, 1973
Buku Teks
Williams, Gareth, author
PSI, [date of publication not identified]
Buku Teks
Allyn and Bacon, 1991
Buku Teks
The officer of Education Research and Development Ministry of National Education,
Majalah, Jurnal, Buletin
De La Salle University Press, 2003
Majalah, Jurnal, Buletin