Saragih, Ondi Gokkon Yanuar, author
Fakultas Ekonomi dan Bisnis Universitas Indonesia, 2012
UI - Skripsi Open
Granof, Michael H., author
John Wiley & Sons, 2013
Buku Teks
Academy Group, 1987
Buku Teks
Darien Aldiano, author
Universitas Indonesia, 2015
UI - Skripsi Membership
Kohler, Eric L., author
Prentice-Hall, 1957
Buku Teks