Longest, Beaufort B., author
Appleton and Lange, 1996
Buku Teks
Northouse, Laurel L., author
Appleton & Lange , 1998
Buku Teks
Bradshaw, Peter L., author
Sage, 2004
Buku Teks
Northouse, Peter G., author
Prentice-Hall, 1985
Buku Referensi
Christoper, Tom, author
Free Press, 1982
Buku Teks