Dittrich, Guy, editor
teNeues, 2006
Buku Referensi
Allysha Tifany Wiranata, author
Fakultas Ekonomi dan Bisnis Universitas Indonesia, 2018
UI - Skripsi (Membership)
Sibarani, Ruth Olivia Laima Natalia Boru, author
Fakultas Ilmu Sosial dan Ilmu Politik Universitas Indonesia, 2018
UI - Skripsi (Membership)
Troxell, Mary D., author
Gregg Division McGraw-Hill Book Company, 1981
Buku Teks
Edwards-Jones, Imogen, author
Corgi Books, 2006
Buku Teks