Artikel Jurnal
Ritonga, Anni Farida
Universitas Indonesia, 2018
UI - Tesis Membership
Hilda Savitri
Fakultas Ekonomi dan Bisnis Universitas Indonesia, 1994
UI - Skripsi Membership
Krauel, Jacobo
Linksbooks, [Date of publication not identified]
Buku Referensi
Garrett, Raymon D., 1935-
Auerbach, 1973
Buku Teks