Perkins, Bradford
John Wiley & Sons, 2001
Buku Teks
Korean Educational Development Institute, 1986.
Buku Teks
Winkel, Steven R.
Wiley, 2007
Buku Teks
Ni Putu Cyntia Suryadewi
Fakultas Ekonomi dan BIsnis Universitas Indonesia, 2020
UI - Skripsi (Membership)
Mann, J.
Clarendon Press, 1980
Buku Teks