Sitompul, Sarah R., author
2013
UI - Skripsi (Membership)
Englewood Cliffs, NJ Prentice-Hall 1991,
Buku Referensi
Helman Arif, author
Fakultas Ekonomi dan Bisnis Universitas Indonesia, 2009
UI - Tesis (Open)
Byars, Llyod L., author
Richard D. Irwin, 1984
Buku Teks
Artikel Jurnal