Universitas Negeri Padang,
Majalah, Jurnal, Buletin
Davey, Graham
Macmillan, 1981
Buku Teks
Klein, Stephen B.
McGraw-Hill, 1987
Buku Teks
Pierce, W. David, author
Lawrence Erlbaum Associates, 2004
Buku Teks
Schwartz, Barry, author
W.W. Norton, 1991
Buku Teks