Cyber Consuslt, 2000
Buku Teks
Legge, John D., author
Cornell Univiversity Press , 1961
Buku Teks
Dian Permatati, author
Fakultas Ekonomi dan Bisnis Universitas Indonesia, 2006
UI - Tesis (Membership)
Humphrey, John, author
A.W. Sijthoff, 1978
Buku Teks
Parrillo, Vincent N., author
John Wiley & Sons, 1985
Buku Teks