Artikel Jurnal
Dilts, David A., author
McGraw-Hill, Irwin, 2007
Buku Teks
Miner, John B., author
Macmilan, 1977
Buku Teks
Yoder, Dale, author
Prentice-Hall, 1962
Buku Teks
Johnson, Rossall James, 1917-, author
[publisher not identified], [date of publication not identified]
Buku Teks