Allen, R.G.D., author
Macmillan, 1973
Buku Teks
Damanik, Difi Sangunan, author
Fakultas Ekonomi dan Bisnis Universitas Indonesia, 1995
UI - Skripsi (Membership)
edited by Gregory C. Chow and Paolo Corsi
John Wiley & Sons, 1982
Buku Teks
Stanlake, G.F., author
Longman, 1987
Buku Teks
Sawyer, Malcolm C.
Macmillan Publishers, 1985
Buku Teks