Bradshaw, Peter L.
Sage, 2004
Buku Teks
Northouse, Peter G.
Prentice-Hall, 1985
Buku Referensi
Christoper, Tom
Free Press, 1982
Buku Teks
Ketchum, Paul A.
John Wiley & Sons, 1984
Buku Teks
Bernstein, Lewis
Norwalk Appletton century crofts , 1985
Buku Teks